I am new to this and need heaps of help, have brought optifast to try and get started, i weigh around 150kgs, need to lose over half my body weight, where do i start ??????

Welcome. Best advise I can give for starters is: If you drink soda, loose it asap!! Replace it with water. Also, make sure you get your 5-9 servings of fruits and vegetables a day. Don't skimp on your calories. For your size go with 2000 cal per day and 30min of moderate exercise. Good luck.

I have started this morning, given up the cola and soda, hopefully i can make it through day one

Same advice as the others, plus change one thing a day for better health. There are great meditations at webmd.com that are good for getting that elusive inner peace. Go to bed on time, do something fun, eat a new fruit etc... You can do it!! And, have plenty of excedrin on hand for those inevitable caffeine withdrawal headaches.