The modem needs no configuration, but if you have a router (most likely you do), that will need some forwarding work.
Go to the router set up page and look for something called "Forwarding". Sometimes this is in the Advanced section. You'll need to forward ports 407 ~ 407 to your computer's static IP address. This may also involve assigning a static IP, depending. You need to do this on both ends if there are routers at both places.
After that all you have to do is set everything up in TB2 under the Setup menu. Make sure TCP/IP is checked in Incoming Access and be sure to set up a user with full acess. Most things there are self-explanatory. The one tricky bit is in Preferences > IP locator. Type your machine's email address in the field then click Advanced. In the Registered Address field type 0.0.0.0 and you should be set.