Okay, not bad, but there are some important details that either you didn't mention, or glossed over. I'll expand on what you said, so you can refer back to this in the future if you need to.
Yes, Ninja are the military force of each Land's Hidden Village, but they aren't just soldiers. They have their own creed, their Nindo's, their Ninja way, which originally derived from Hagoromo's teachings, Ninshu. Over time though, this creed was corrupted, and became what Ninja in the present refer to as Ninjutsu, which we Ninja are able to perform utilizing Chakra. Chakra was originally a gift to the world from the Sage of Six Paths himself, allowing every living being on the planet to access a wealth of strength within themselves. Chakra is created by moulding two forms of energy together, Physical Energy, and Spiritual Energy. I personally believe that humanity always had Physical Energy, as it is described as an energy that is present within every cell of every living organism. It's essentially any individual's life force, and provides the physical aspect of Ninjutsu. If you overexert yourself in your usage of Jutsu, and deplete your Chakra stores over the course of a fight, and thus have no Physical Energy left, you will die as Physical Energy is the very life force that keeps you alive. Physical Energy is strengthened and increased through physical training and other rigorous forms of self-enhancement. The other kind of energy is known as Spiritual Energy, and is more closely tied to the user's imagination than any physical action. As such, it is strengthened through study, meditation, and other such spiritually fulfilling experiences. By combining these two together, we achieve what's known as Chakra. Chakra flows through our bodies like blood, and has it's own delivery system, akin to how the circulatory system delivers blood to your organs and the rest of your body. And Chakra, as you stated, can be used in a seemingly infinite number of ways, which is almost always achieved through Shape and Nature Manipulation. Through changing Chakra's shape, we can achieve amazing effects with our Ninjutsu, with techniques like the Rasengan utilizing extreme levels of rotation to buffer and blast a target to shreds, without any other form of enhancement, just pure manipulation of it's physical shape. Meanwhile, through the usage of Nature Manipulation, Shinobi can change the very nature of their Chakra, allowing them to expend Chakra in order to create entire oceans of flame, or make nature itself bend to their will, with Kirin being one extreme example, utilizing Natural Lightning for ungodly levels of destructive capabilities. Fire Release is one such example of Nature Manipulation, and it is achieved most easily by gathering one's Chakra within the stomach, and super-heating it until the Chakra itself changes it's Nature. Once combined with the user's breath and exhaled, or even by releasing it from Chakra Points found throughout the body along the aforementioned Chakra Network, the user can release waves, orbs, streams, walls, blasts and other such amazing forms of Fire. Some Clans, like the Uchiha or the Sarutobi even take their usage of the Fire Element to entirely new levels, creating fire strong enough to alter the weather itself, or encompass a landscape the size of a Village, or even take new forms, such as that of combusting/ explosive ash, which is the Sarutobi Clan's specialty. In conclusion, Fire Release is but one small part of the expansive field known as Ninjutsu, and one of 5 Basic Elemental types of Ninjutsu but it is one that I personally prefer. Do you have the same constitution for enduring searing flames, in order to control this wild and primal Element? Let's see, shall we?
I reach into my Ninja Tool pouch, and pull out a small pile of seemingly normal slips of paper. I pull one out from the bundle and hold it between my index and middle finger, simply keeping it there, without any physical motion of any sort. After a moment or two of being held between my fingers, the slip of paper suddenly ignites, combusting in a dazzling display of reds and yellows that burn brightly for a few seconds, before the slip burns away to ash. I hand you several slips of paper, and give you your first objective.
"Before you can perform Fire Style Jutsu, you must learn how to create, then channel, Fire Style Chakra. The slips of paper I handed you are what's known as "Litmus Paper", and is made by growing and harvesting a special type of tree that feeds on Chakra. By gathering and channelling Chakra into this slip of paper, you can train yourself to become more and more proficient with the moulding and channelling of Elemental Chakra. Start by simply letting your Chakra leak into the paper, once you get the hang of that, try focussing on the Chakra that you leak into the paper. Focus on the heat coming from the sun, or the heat from your own body if you have to, but the more you focus on heat of any sort, the more easily you should be able to gather and stream Chakra into the paper, while simultaneously heating it, before it finally combusts, like mind just did. Once you achieve that, you'll be at the stage where you can perform the most basic Fire Release Ninjutsu. From there, your aptitude for this Elemental Nature will rapidly snowball, possibly out of your control, until you reach a point where you can create flames that deal widespread destruction, and it will take nature decades, even centuries, to recover. But for now, you have to focus on simply creating a flame. After all, you've gotta learn how to walk before you can run..."