Q. Chess: how to make castling?
A. When you tap king, the app shows regular king moves (1 square long) and also castling moves (2 square long). Tap on a proposed move to make castling.
Note, that castling is prohibited by rules if you have already moved king or rooks, or when castling figures are under attack before or after castling.
Q. American Checkers: why the app does not allow to make the move I want?
A. The app follows official rules (american checkers/english draughts/german dama) and does not allow moves that are prohibited by rules. For example, officially, capturing is obligatory when capturing is available. If you don't want to follow official rules and want to have free choice of capturing, please, set "Forced Jump" setting as OFF in the app settings.