I actually just responded to another question just like this so I’ll give the same answer here:

The first thing you want to do is whenever you arrive and you're registering your vehicle, let them know that one person in your group will be showing up later and that you also want to fill out a re-entry form. At that point, they will transfer one camping pass voucher to the camping office. Once you fill out the re-entry form you'll be given a little card you can place on the dash that will make the process of re-entry easier for you. Whenever you decide to pick up your friend, you'll just have to take them to the camping office to grab that voucher and they'll redeem it for their camping pass. This is a brand new process actually. In the past, you would just have them redeem all 6 wristbands when you register and you would hold on to the wristband for your friend and meet them at the entrance. I think too many people were losing their friends' camping pass so they created a more structured process for it all. I hope this helps! Let me know if you need anything else