Camping questions

Do I have to be in the car entering the campsite to get the camping wristband or does a car entering get the allotted amount? I’m not sure if I can go on Friday with my brother that’s camping.

If I go on Friday with him, am I able to get a wristband then uber out to my car Friday afternoon/night? Then just park somewhere in Fontana or San Bernardino and Uber back in?