All that should be necessary is to copy the file you're trying to restore (e.g. "Smith Family.ftmb") into the virtual C: drive of the VM. Then when you restore it, make sure you're selecting a location on that virtual C: drive in which to place the tree.
I run FTM2012 in VMWare Fusion, mostly for troubleshooting problems from the forum or to help out family members who use the Windows version. However my personal tree is in FTM Mac 2, which after the most recent updates has "almost" every feature from FTM2012 and even a few benefits (e.g. able to directly create PDFs of more than 200" dimension). You might look at switching to the native Mac app.