Take the top horizontal match that is second from left. Place it diagonally within the top left square (like so /).
Take the horizontal match that is directly below the first one that was moved and place it diagonally in the top right square (like so/).
Viola! Four equal squares!
Ha! Good try. You actually moved one of the correct matches. Just not into the right place. Take the first match you chose and place it vertically directly below the match dividing the first two squares on top. Then slide the bottom match in the left square on the bottom directly to the left to complete the square you just started with your first match. See?
I always get so confused with these. 😀