lol xD I thought you knew this... well
Step 1: Save the gif picture/smiley in your desktop or what ever you want to save it.
Step 2: Then when you have saved go in your messenger chat click on the

smiley then all of your smiley's will show up then click on "Show all" in the right side.
Step 3: When you did that now another place will show up click on the thing called "Great" in the right side.
Step 4: Then you have to find your smiley/Gif picture at your desktop click on the smiley click open.
Step 5: the first line says what key words do you have to writ before the smiley will show up this is a example "lol" then when you writ lol your smiley will show up in the chat simpel and easy the last line call it what ever you want just writ everything you want ^^