Turns are broken into two parts, movement and combat. In both of them, click on the relevant unit to bring up possible targets as white boxes (either spots to move to or shoot at) then confirm all moves with a Yes or No. Lots of confirmations, actually... each turn requires a yes or no as well. The game appears to have a nasty bug where using the load function doesn't properly clear the impassible flag on bridges, making it impossible to progress.