Using the keyboard:

You can move the player using the arrow keys for moving the player up, down, left and right.
Alternatively you can use the keys: w, a, s, d or i, j, k, l

Using the mouse:

Click at a free position to let the player move to that position.

Click a box to select it and then click at the target position for that box to let the
player push that box to that target position.