Enemy moves/attacks

I am making a game called Silent shadow. I have only started it and I need help to make enemies to move and attack randomly (like an NPC).Has anyone got any advice to help me with this? By the way, in this game there will be multiple waves and enemies.

well, you don’t lose any lives, good work on the gun mechanics, but that’s all I know.

OK, all I need to work out is how enemies attack and do stuff randomly