Riding toeside is a great progression when you have mastered staying upwind. Infact, it is probably most rider's first 'trick' they try.
You'll also need to lock in riding toeside before you can try landing any jumps toeside.
Ride along with speed. You will need to maintain speed throughout the transition and beginning to ride toeside. If you find you are stalling and sinking in the water riding in with more speed may be the key.
You can either pop into toeside or just slide. At first you may want to practice just sliding to toeside. To slide into toeside bend your front leg and slide your board around nearly 180 degrees. You should be pointing slightly further down wind to get your speed back up and keep sheeted on or dive your kite to mainting power and speed. Once your back up to speed you can focus on staying upwind.
The key to riding upwind is to distribute your weight onto your toeside edge. To help yourself balance release your front hand from the bar and use it to steady yourself. Releasing your front hand will also open up your shoulders and turn your hips away from the kite, making it easier to keep the board's toeside edge under pressure.
The more powered you are the more pressure you can put on your back leg. If you are in lightwind your weight should be more evenly distributed between your legs. Bend your back knee so you can put as much weight on your toes as possible.
To return to heelside either slide the board back around or bear away downwind into a transition and ride away heelside in the other direction.
You just nailed it!