Installation is simple:
If you included the 393 extensions from the suggested config, you can dial any number within FWD by using that prefix. For those that didn't pay too close attention to what they were cut&pasting, here's the example from FWD:
exten => _393.,1,SetCallerId,${FWDCIDNAME}
exten => _393.,2,Dial(IAX2/${FWDNUMBER}:${FWDPASSWORD}@iax2.fwdnet.net/${EXTEN:3},60,r)
exten => _393.,3,Congestion
Think of 393 as an area code, where you dial it to access numbers in FWD rather than the State of Florida. By dialing 393612, you connect to FWD automated time service (the IVR reads you the current date and time). "_393." means "393 followed by any other numbers" and "/${EXTEN:3}" means calculate the remote extension number starting with the 3rd digit (remember, programmers start counting with "0" so there is a 0th digit).
Here are some other useful (or not) numbers within FWD:
511 Conference Bridge 613 Echo Test (Test quality/latency of your connection) 614 Milliwatt test (For true technical types) 615 Voxeo Tone test (Enter '#' to try a different tone) 958 Number Check 514 FWD Coffee House Conference Bridge 55555 Welcome Line Conference Bridge
FWD also maintains a list of peer providers to which you can connect from FWD for free.