I don't think you need to be approved in the regular RP section. You can just submit a character and have at it. Of course you have to go to the OOC section and look for open RPs to participate in any, or you can plan one yourself. Really, it requires coordination between members to work effectively.
However, in the "Equestrian Empire" section your OC needs staff approval. Just submit a well detailed profile in the appropriate section and if it is not marked as WIP then one of the RP Staff members will look at it. Of course be sure to read the rules of course in regards to how the profile is to be properly structured and typed.
Just be sure to go the respective OOC sections and read the rules. You'll be set afterwards I think.
Roleplay OOC
EqE OOC
Of course do not be afraid to get in touch with the respective staff members for any questions you may have.
Ashen Pathfinder's post in Leaving Permenantly was marked as the answer