To the OP: if you dunno how to throw, you can always just try to resist the throw of your opponent. It is easier to play 100% defensive than to try to fight for the win.
In stand-up grappling like bjj, judo or wrestling, you should stop your opponent to get grips on you, by moving, grabing its hands or breaking its existing grips.
If attacks on legs are possible, watch for sprawling the whole time.
But be cautious, to be overly defensive is not the way to go. If you run backwards the whole fight, you will not learn anything. To learn something, you must let the opponent start to fight at least a little.
For example let him get one grip, but fight the second. Let him attack the legs, but be ready to fight for the sprawl. Try to really block him: grab its two hands and stop him to do anything. It will annoy him and force a reaction. Watch how your feet are posted on the ground: if you and your opponent have the same leg frontward, the position is offensive for both of you. If it is the opposite, it is a defensive one.
I know I’m going to get flammed for this, but you dont need to learn techniques to sparr. One can start with basic defensive concepts.
Dont believe the hype: before being able to use in sparring the techniques you have seen in class, you will need a LOT of time.