FVS318 router setup

I have 2 FVS318 that were talking across the Internet. Someone else set it up.
Now I was asked to “fix” one side where the router was reset. I need instructions on how to set it up. The RPC icon still exists on the computer but of course its information will not work until the VPN is setup. It was attempting to locate a 192.168.1.10 computer in another state.
Can anyone please give me step by step on how it’s done? What info do I need from the working VPN on the other side? Thanks.