there is oodles of different software out there. id do some reading and research into some of them and pick one that best fits your project. Thats all the advice i can offer up.
trial and error i guess.
i started out on Cool Edit Pro. Its light and easy to use.
Im now using Sonar 4. it was a pretty easy switch to make.
To get your feet a little wet to digital multitrack recording, and to keep from investing too much right away, try a program called "Reaper" (just google it) it's free to try and very very cheap to buy if you like it.
If you're that new to computer recording, go with Audacity. Simply the easiest, most straight-forward program to use and it's cross-platform.
Once you learn the basics of how digital multi-tracking works on a computer (adding tracks, setting up the preferences, arming for record, effects, etc), then move on to Reaper.