No disrespect intended but your question is very vague. Its like asking what do I do in a boxing match other than not getting knocked out. The answer is everything. That being said I'll try and give you a place to start.
1) Focus on technique, not strength. What I mean is; watch and look for leverage and balance points. Where are your opponents posts? Are you overbalanced or too high?
2) Work on being in control. Control your opponent's, (and your) position and posture. This takes time to learn. Start with controlling their head and hips. Expand from there.
3) Learn single and double leg takedowns. Again, this will take alot of time and practice.
4) Learn takedown defense. Underhooks and crossfaces are your friend.
5) When you get some of the basics down, ask someone to show you leg riding techniques.
6) Cardio is more important than strength.
Since you're just starting, expect to get owned for awhile. Try not to get frustrated but lose the ego and learn. Ask alot of questions.
Good luck and have fun.