I dont know how to say it any clearer than Itachi how said it ;
Once you decite to use it you need to ;
Spot a moment, where you're aware of your chakra / senses but also your opponent's chakra and sense ;
- this mean that you need to have a moment where you can exactly tell how you and your opponent were feeling like
- In Itachi vs Kabuto's care, Itachi had that moment when he engaged in close quarters with Kabuto when he cut his horn off
From this point on, Itachi's goal was do have the very same situation happen again so that he would be able to connect the first time he had that situation happen with the second one.
How exactly does the ''connecting'' work, i have no idea. But what happens is that Izanami stucks the victim inside those ''Identic situation'' until the victim decides to accept his true self.
It also seems not everybody is vulnerable to such technique, Kabuto was although, and it seems that any Izanami user also is, so it would mean Obito also is... and given the circumstances of his devellopement, i'd have to agree that Obito doesnt belong to where he is just like Kabuto didnt belong there either, which is why Itachi wanted to cast Izanami on him so that he wouldnt fool himself and follow a path that isnt his.
