Most instructions are in the game. Try to hit the other paintball player by aiming your paintball gun at whichever bush you think they're hiding behind (with arrow keys). You then press space and hide behind whichever bush you want (with arrow keys), press space again, and see what happens! Press space again to shoot again. Press E at any time to go into streak mode, which makes it so you get extra lives per win.
Credits: Song: Upwind by TheFatRat - Check him out on YouTube, Spotify, Soundcloud, and more!