workouts p90x

With the P90X workouts can i add a couple of sets on the bench press and preacher curl?

You could always do your own extra thing, BUT here’s the thing…
The workout is an hourlong, you go any further and you start taking the risk that you’ll be using muscle for energy, meaning that it will deteriorate and vanish.
Also, even if you are trying to bulk up, the muscles of any group (back, chest, legs, bicep. etc) are not supposed to be worked out over an hour or it causes an anti-catabolic effect, meaning overtraining, meaning your muscles will not grow.
Stick to the program exactly how it shows you.