Some tips that might help assuming you are already flying the rig:-

1. Keep your hands fairly close together on the boom and your arms straight.
2. Place your back foot on the back of the board...just with your heel. Its primary job is to control the position of the board and specifically to drag the back of the board towards your backside.
3. In light winds angle the rig so that the nose of the board is off the wind. You do this by pushing the boom and therefore the luff of the sail towards the nose of the board.
4. Bend your back leg so that your heel pulls the board towards you right up close to your backside..........keep your front leg straight in the water.
5. Now is the time to explode up onto the board........get your head so that your arms are touching your ears so that the boom is directly above your head. Now at the same time, kick with your front leg and use your core to explode upwards.....within a split second the rig should be sufficiently upright to enable you to also pull down through the boom. Don't straighten your body until you are fully up and over the board.
6. Place your front foot close to the mastfoot...both feet should be close to the centre line of the board.

If you do not understand "using your core to explode upwards".......it is like jumping but without using your legs. If you have done any rock climbing it will be second nature.