Use the left and right arrow keys to move the falling block sideways. The up arrow key rotates the block, and the down key drops the block. If you're holding down the shift key while pressing the down arrow the block will drop but not stick to the floor, thus giving you some extra time to move it sideways. Holding down the control key while pressing the down arrow will make the block fall faster but not dropping all the way to the floor.
If you wish to send spogglings to other players you may use either the mouse to click on their screen or the F1 to F4 keys. Pressing Esc will remove a falling spoggling if you do not wish to send it to an opponent and F5 will bomb the leader.