To move a frog or a toad, just click on it. There's no need to click and drag to the space into which you want to move (why?). If the piece cannot move, then nothing will happen. If it can, then it moves into the empty space. In this version of the game, the toads cannot move to the left, and the frogs cannot move to the right, so think carefully before you move.
When you have solved the problem (or when you are stuck), you can click "Play Again!" to start the game over. After mastering 3 frogs and 3 toads, try changing the numbers before you select "Play Again". Any numbers for the frogs and toads will work provided that there is at least one frog and one toad, but not more than twenty total critters at a time.