You can set the dice for a player by clicking in the middle part of the board where you usually click when you roll the dice while playing. Click in the middle of the right playing area to set the dice for player 0, the bottom player. Click the left dice rolling area to set the dice for player 1, the top player. Once you click one of these areas the dice selection widget will appear and you can select a dice roll by clicking on a dice pair.
Click inside the red rectangle to set the dice for Black. Click inside the green rectangle to set the dice for White.
Setting the dice in edit mode sets both dice and the player on turn. Setting the dice for player 0, will make player 0 on turn with that specific dice roll to play.
This method for setting the dice roll only works in edit mode. If you're not in edit mode you can set the dice by choosing Game->Set dice... from the menu, however this will set the dice for the player on turn.