Menu above: Edit > Settings > Playing 2 Tab > Under 'Move Assistant' uncheck 'Always promote to queen'.
When checked you will automatically get a Queen when your pawn can promote
When unchecked you will get a small pop-up window appearing when your pawn can promote. It will be asking you to select a Knight, Bishop, Rook or Queen. Select which you want and press OK.
When you have decided if you want ‘Always promote to queen’ on or off, press OK.
Alternatively you can keep Always promote to queen turned on but when you want to move a pawn to promote but rather have a Knight instead of a queen you use the command method.
Lets say you want your pawn to move to e8 and become a knight. Type on the command bar: /e8=N This will move your pawn to e8 and turn it into a Knight. (Knight = N, Queen = Q, Bishop = B, Rook = R)