Hi Eugene,
A 12 user license will allow 11 concurrent users behind the WinGate server to access the VPN. It doesn't regulate how many joiners you have (from external connections) as this is regulated by the license at the remote end.
As long as you have the default gateways of the client machines pointing at the WinGate server then you don't need to install any further software. If you can't point their default gateways at the WinGate server and still want them to access the VPN then you should install the RIPv2 Client, available from our website for download (
http://www334.pair.com/qbiknz/downloads/ripv2client.zip)
If you are going to install WinGate in another office then you will need to purchase a separate license for that machine. You will also need a VPN license for the remote end of the VPN.
Regards,
Matt