Redundant pair by adding a second BIG-IP VE to an existing system

@Soda Cup, I already have one functioning Big-ip that I set up some time ago. I am fairly new to F5 configuration. I am uneasy about how to juggle the IP addresses that are already configured for the first device in with the new IPs for the second device, and how to create shared IPs. talks about that, but you say its not up to date.

Your article only talks about creating a redundant pair starting from scratch, not about adding a second device to one that is already working well. Is there a procedure somewhere that spells that out?