Changing Battle Sprites?

I know this isn't really on topic, but how do you create a Character sprite? I create them and put it in my folder. But when I try to put it in the Game I can't because of Colour Depth, I've red other posts and tried everything! http://charas-project.net/. And its the same with Face's and Battle Sprites!

I'm stocked man'

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P.S I'm a Dunce, how do you set an Avata.