Perms for specific skin group?

I am running DropVehicle which gives you a supply.signal to throw and it is supposed to give you a vehicle (RHIB, Minicopter, etc) when you throw them. Thay are coming down as regular supply drops. I am trying to work through this. I have added their respective skins to your plugin but want to know if theres a way to add a permission to a specific skin group (supply.signal) so players can't reskin a regular supply signal to a vehicle drop. I see a permission line in the config but am not sure if this is how its done. What would I put in the quotes and how to add the perm to my server? Any help would be appreciated. Thank you in advance.

you should put the perm in quotes, just like it says