Hi
Basically, you install WinGate VPN on one machine in each LAN, pick one to be the VPN server (so in its config, set up a "VPN to host"). In the other VPN installation on the other LAN, you would set up a VPN to join. The easiest way to do this is to export a config from the VPN to host, and import it into the joining VPN installation.
If you are connecting in to the hosted VPN through another firewall, on that firewall you would need to forward the VPN ports - usually port 809 UDP and TCP to the machine behind the firewall that is the VPN hosting machine (usually called the VPN server).
If you are using dynamic DNS, then enter the DNS name of the VPN host machine in the joining VPN.
There is a good document available in our resources page for this as well which goes through step by step.
See
http://www.wingate.com/files/VPN_Setup_Guide.pdf for more info
Adrien