First time juicer

Hello everybody! I just bought a Breville juicer and i'm about to start juicing for the first time. I wanted to get some basic info that might cater to me because i'm a bit different from most people. I am 6'10 and weight 260 pounds. I am a former college basketball player and my playing weight was around 230-245. I'm looking to drop down to about 230 again. My main question is how much juice should I be drinking if I want to replace a meal? Also, is it bad to make juice and keep it in the fridge, or do I need to drink it fairly soon? Any other tips and tricks for a beginner would be greatly appreciated.