By clicking on "Drag pieces" or "Click on squares" you can decide yourself which system of move input you prefer.
Drag pieces: while clicking a piece, the mouse cursor will change into the piece and you must drag the piece to the destination square Click on squares: while clicking a piece, the mouse cursor will not change and a second click on the destination square will finalize the move input.
This function is NOT available if you do not have a VESA-compatible card. In this case Rebel will only accept "Click on squares".
HINT
Try both systems and judge for yourself which is convenient for
you. Please note that "Click on squares" is a faster way of
inputting moves and this is especially handy on blitz games.