First, if you don't have a free parking pass that's printed and in your possession at this point, you'll have to carpool with someone who does, because they're all handed out. Next, if you're in possession of a parking pass, gates open at 9 a.m. Sat. 4/20 and Sun. 4/21/23 so, plan to get in a line of traffic to get on base ASAP in the morning because you only have until 1:30 p.m. to get in, before officials REVERSE traffic to only allow vehicles to LEAVE the show. Everything you need to know before you go can be found here
Flight demo's start daily at noon, weather permitting, and AF Thunderbirds close shows both days, which ends at 4 p.m. Take a look at the Charleston Air Show's updated layout showcasing the static displays and vendor locations:
Also, sounds like you shouldn't bother Uber/Lyfting per JBC recommendations, drivers likely won't have a parking pass to get you in nor will have any way to pick you up when Air Show ends at 4 p.m.
So, hydrate, slather on the SPF and hats, be safe and have FUNNN!!!