The next step is to get a SIM card. Verizon will give him a SIM card with his name and number on it. This could be an advantage or disadvantage depending on whether or not he wants to be reached on that number while overseas. He could also get a local SIM card with an Italian number. This might also save him some money because he can buy data there too. Since he's going to Paris and Amsterdam, he might end up with a SIM card that will work in one country but not the other. He might want to get a SIM in France and in the Netherlands.
Because it's an iPhone, it's very popular everywhere. So it should be an easy enough process to walk into an Orange or TeleFrance store and they should know exactly what he'll need.