RDP and/or VNC to remote network's computers

What is the easiest/most simple way to use the Dude to connect to computers within a remote network? I already have an RDP/VNC Tool added to The Dude, but of course it only connect to outward-facing IPs.

What about a VPN?

How is the remote network connected? Are they on thier own ip subnet? Once you created a vpn to it you could rdp to them.