Becky
Think of your inside leg as a pivot or fulcrum around which the horse bends. The inside leg is right at the girth (or cinch), just behind. It's a supporting leg, not an active aid, so you have the entire leg laid against the horse's side, pressing as needed. The outside leg goes farther back behind the girth (not enough to throw your upper body forward!); I pivot the outside toe out slightly to make sure my spur makes contact - but I DON'T turn my heel all the way in and dig! At the same time, bend the horse's head in with an intermediate rein on the inside.
Once you achieve the bend, use your inside leg pressure AT the girth to press the horse forward into the outside rein - but hold the outside rein so that the energy shoots forward through the bend!
Is that clear as mud? If you have any questions, ask away!