what do I need to do to get permission?
Join the club :)
In the meantime, as @LinusR says, just rock up at 8.20am and introduce yourself, you will quickly be pointed in the direction of a suitable ride. Do make sure you read the group riding guide first though - lots of important safety stuff in that.
There is also a more formal Introduction Ride which happens monthly, with limited spaces. Here is the link to that thread, which you will be able to see