I installed Worms World Party but its not detecting my custom maps. I also like to know which directory the custom maps go into?

Same as WA, custom monochrome maps go into the \User\SavedLevels folder (and you can't use subfolders, everything has to be in the root folder). But WWP doesn't support the PNG format natively, so you'd probably have to look into things like CutWorm for that:

http://worms2d.info/CutWorm