You'll have to do more than just determine the BPM for the song, because it probably varies unless it was recorded to a click.
AudioSnap can create a tempo map that will adjust to any tempo changes. However, how good a job it does depends on what you can give it to analyze as a reference.As Rocky says, a kick drum works best. But if it's just guitar, or worse, guitar and vocal on the same track, then AudioSnap is going to have a hard time figuring out the tempo.
If that's the case, you might try creating a click track by hand. Record a hi-hat sound using a MIDI keyboard, playing along with the song. Because you're recording MIDI it'll be easy to nudge notes as necessary until the hi-hat's playing along in good synchronization. At that point you can route the MIDI to the TTS-1 and freeze it, then have AudioSnap create a tempo map based on that click track.