Hi Amphibian,
If your Elastix GUI is in english, the EasyVPN addon will show be shown in english. The addon takes you step by step to setup a fully working VPN. If you have any problems just hover your mouse on the ? marks and you'll se a help message.
It's really simple, but as danardf states, you'll need to open up a port in you firewall and redirect it to your server, that way your clients can conect to your server an create the tunnel.
Hope you like the addon, your coments would help us make it better.