Drag your finger to move and push blocks. Line up three keys of the same color to open the lock of that color. Keep pushing and matching to open a path to the portal.

On later levels, you can line up 3 blocks that show the four-directional arrow symbol. This will make all arrow locks move in the direction they are pointing. 

If you get stuck, you can use the on-screen buttons to undo your last move or restart the level.