I want to create a game similar to sea battle 2 ! how can i do in ue4?

If you’re making it 2d I won’t be able to help you, not my field at all. The docs are here:

And there’s plenty of tuts online. One advice I can give is: do not try to make an entire game in UMG, it is seriously limited and you will not be able to handle logic comfortably.