I need some advice.

Hi everyone. I have been in this reddit community for a bit but never actively participated but after seeing the results and progress of others, I want to try it. (Very proud of everyone by the way!!) I am a 19 year old female and my BMI is 40.. I hate it and have tried dieting to exercising but nothing seems to work. Can anyone offer tips on how to start fasting and what to do during my fast?