How to mix my boxing and weight training to together?

I train in boxing from 4:30-6:00 and may be starting 6:00-7:30 or 4:30-7:30. Idk yet (5 days a week/no week end).But either way, we do calisthenics and bag/mitt work during practice. No weight training included. With summer starting, I will be able to make it to the gym at any time of day so I can catch up on my weight training. But I have heard about over training. How do I stay away from that? Should I not go to boxing on the days that I weight train (1-2 days a week/not including weekends)?