ok so uhh basically
first you have to think of a challenge (for example: draw [character]) and then (this part is optional) you would think of a deadline (for example: october 17th) and you can also put rules like no inappropriate stuff in it and/or put a certain tag like #cheeseballs in the description so u can find the post
and after the challenge ends you can choose the best drawing (or top 3 drawings) to win and get a prize like fan art where you draw their character
and if u want you can draw an example of the challenge (like if the challenge is to draw your character as a cat you would draw ur character as a cat as an example)
hopefully I explained everything well I’m kinda bad at explaining things