There are 2 Levels of programming (Engineer and Admin), and you have just revealed your admin password to all in a public viewable forum, which is probably not a good idea.
Dial Admin Code means - dial the code associated with the programming step you want to change, refer to your BT Revelation Owners manual or "call a man in".
Its going to take me too long to tell you step by step how to do every single one of these changes "step by step", basically if you have no idea of the programming, read your manual (if you have one) or get someone in if it is urgent.
I don't mind pointing you in the right direction but thats a bit of difference from step by step which is going to take me some time to type out to someone with no programming knoweldge at all - and I am not going to do all that in a public forum anyway.
All extension programing is controlled by the BLF lamps (on or off to set the extension).
Simon