You can enter the tombs at the right side of the Basilica, after a tour you climb up the stairs and you’re inside the Basilica. The tomb of John Paul II has its share of devotees in front of them. He has a plain stone, not like many of the richly decorated tombs of the others.
Don’t forget to cover yourself (same rule as the Basilica) and take of your hat – my boyfriend kept forgetting this so we kept getting scolded by the guards.