This is a 4x4 version of Reversi. Also called Othello. Instructions below.
Place your piece on an empty square so that one (or more) of the opponent's pieces are between yours.
Here Red is about to capture a Blue piece ...
... and it is now captured, becoming Red.
You must capture ... they are the only valid moves. If you can't capture, then you lose a turn.
You win by having more of your pieces than the opponents at the end of the game.
There is lots of interesting strategy in this game! Sometimes you seem to be winning then suddenly lose at the end.
I don't want to tell you too much ... it is more fun to discover new things yourself.
Keep trying and you may one day beat the computer!