Try and find a bit of chop or a wave, say 15 metres ahead of you, in other words pick your jump. Head slightly downwind and now place your hand at the rear of the boom, the further back the better when you are learning. Jump off your chosen bit of chop and turn your board downwind, you do this by lifting your rear foot under your bum and sheet in hard whilst looking towards the clew of your sail.
Whatever you do NEVER look straight ahead or down at the water when your doing a loop always look back over your back shoulder as far as you possibly can.
Keep sheeting in hard, even just by holding this position you will rotate a certain amount. You can tell just how far you have rotated by looking at the clew of your sail. It’s very important to not sheet out or let go of the boom with your back hand at this stage as you will probably be in for a hard crash.
Initially you will land on your back, but over time and with practice you will get a feel of what a loop feels like and will develop your own technique.