I'm a beginner and want to know how long should I practice each time and how many times a day is ok before I cause more damage than good? I'm using Jon Stathom's beginner course. 

Hi, Timothy!

I'd start with 15-20 minute practice sessions, 1-2 times per day. If you're feeling good and aren't experiencing vocal fatigue, feel free to increase your practice time! With voice lessons, you're learning and practicing new coordinations. So it's really about returning to that coordination over time, until it becomes muscle memory. A shorter amount of practice every day is better than an hour or two of practice in one or two long weekly sessions. 

Good luck!