Bit late but a couple things I always hear being said to beginners;
-try not to use brute force. Will be difficult without knowing many techniques, just bear this in mind.
-tap. Forget pride, forget seeing how long you can resist, when you're caught learn when to tap. You'll learn quicker and will less likely get injured.
-escapes and improving position is way more important than learning submissions at this stage.
-focus on simple techniques/drills involving hip movement (e.g. upa, shrimping - google/youtube these).
-keep practicing the drills in class rather than stopping to talk or sit and watch others.
-pace yourself. even if you're fit your body probably won't be used to the kind of movement involved so take it easy and relax