what behaviour are you using to move your sprites?
Are you using the mouse or the keyboard to make the player move?
Will the player be able to go diagonally or only straight?
will the player be able to set destination further away than one grid-move?
grid-based movement can mean a lot of different things to different people. In the FAQ there are some links to topics where people have tried. Using the search function you can find even more topics.
Basically it's setting the destination of movement based on the size of your grid.