Moving from a local HA configuration to a site-site HA configuration

Hello,

I have two F5 appliances in HA mode at the production site and we are using an ethernet cross-cable to implement the High Availability between the two sites.The customer needs to move one of the appliances to disaster site and implement the F5 HA scenario between sites.

Can somebody pls advise of the stepwise procedure and configuration and what we need to take care for moving from the local HA scenario to the two site HA scenario ?

tx BR