I've seen vehicles with decals saying PlanetSide Beta and others. How do I put one of these decals on my vehicle? And how do I get some more?
To apply them, open the pause menu, go to the vehicle tab, select the vehicle you want to customize, and choose a loadout:
Then pick "Apperance":
Then go to the decal tab, pick the decal you want, return to the game, and spawn a vehicle with that loadout.
To get more decals, click "Get More".
That will take to you to this screen where you can filter to decals and unlock ones that you want for Station Cash:
Alternatively, you can buy them buy just going to the store tab and picking "Vehicle Gear":