As it stands now, you need to use a separate program. IVM doesn't have any built-in faxing capabilities. It does however have a handoff feature that will let other faxing programs receive data calls that come into the modem while letting IVM answer the voice calls.
I can't think of / suggest a program off-hand though, but you'll probably need one that supports answering calls from a tapi handoff.
By the way, if you would like a Free fax number in the US, I can tell you where you can get one (you get a free private number for people to fax to, and faxes are sent to your email as a pdf). Unfortunately the number would not be local to your area.