You can not use a cambered sail without cams ( unless it is one of the very few convertible sails with traditional luff pocket widths.
Outhul dowhaul as explained but for general sailing/ learning and developing your skills i would stay clear of any cammed sail.
they were all the rage many years ago but these days a good soft sail has only a few knots less speed and farrrrrrr! better ease of use, especially if you are new to the sport.
But for free, might as well give them a go.
cheers