Instead of reviewing one by one the main 4 attractions in Provins, I would just say that they're all worth it and you can visit all of them with a pass for only 11.40 euros. Each one of them provides you with a better idea of the town's rich history which could be very interesting if you're into cultural tourism. I visited Provins on a Friday afternoon and then went back on a Sunday because I loved it. My visit on Sunday was better since it was very quiet. If you want to see all the attractions with your pass and maybe do one of the Medieval shows I suggest you come very early and check the opening and closing hours for each one of them because they vary depending on the days. If you don't want to visit the attractions then you could just walk around and visit the stores selling products from the region or eat at one of the cafés or restaurants located in the Medieval part or the newer part of Provins. This could be done in a couple of hours, otherwise plan a whole day for your visit.
To get there from Paris you need to go to Gare de l'Est and take a train to Provins (located in zone 5) if you have a pass covering all zones then you don't have to pay anything extra. It takes about an hour from Gare de l'Est and I believe there's a train every hour. When you arrive to the Gare in Provins, cross the street and you'll see a sign for the "Office du Tourisme - cité médiévale" indicating which way to go (if you want to buy your pass and get information) keep walking until you come across another sign, follow that direction until you see a set of stairs, go up the stairs and keep walking until you reach a square (Place du Châtel) that's the main area in the Medieval (and older) part of Provins (here you could ask around where the Tourism Office is or try to find it following a third sing located at the end of the square on your left)
The problem with the Tourism Office is that is not even inside the Medieval town, so tourists have to pass by the lower and the upper part of the town just to get there (ridiculous!) By the time you find it, you have already seen the main areas and buildings, guess they didn't think about it beforehand. If you don't need information or the pass then please start enjoying from the moment you exit the Gare :)