To win Squadro, you need to be the first player to make a return trip with four of your five pieces.
Each player starts with their five pieces in troughs on their side of the game board, with players sitting perpendicular to one another. When you move a piece, you move it a distance based on the strength indicated in the trough that you're leaving. Once the piece has made its way across the board, you move it back based on the strength on the other side. If you pass over an opposing piece while moving, then that opposing piece must return to its base.