Hi!
So the game is all about figuring out the name of the demon in front of you (press summon to show the first one). The demon catalog on the right contains clues you must use to identify the demon. When you think you've found the right name, click confirm the name. So for example, if you think the demon in front of you is Belzebro, have that page open and then click confirm.
If you were right, the demon will go away. If you were wrong, they'll mock you and you won't be able to guess another name for half a minute.
The game ends after you find the name of 5 demons.