Provins is 80 kilometres southeast of Paris and easily reached for a day trip.
By train, take the Transilien Line P from Paris Gare de l'Est. Trains run roughly every hour and take about 1 hour 25 minutes to reach Provins station, at the foot of the lower town. The walk uphill to the upper town and the main sights takes 20 minutes (steep in places); a free shuttle, the Provinois, also runs between the station and the upper town on weekends and holidays in summer.
By car, take the N4 east from Paris (or the A4 to exit 13 and continue on the N4) — about 90 minutes in good traffic. There are several large car parks just outside the ramparts; pay parking is enforced from April to October. Don't try to drive into the upper town itself: the streets are narrow, congested, and largely pedestrianised in summer.
Day trip vs. overnight: Most visitors come for the day. If you want to attend the medieval festival or one of the evening shows, staying overnight is worthwhile. Hotels and chambres d'hôtes inside the ramparts are limited; book in advance.