Looks like what you're missing is a preamp for the mic.

Either a standalone preamp or a small mixer will work.

art Tube mic pre is pretty inexpensive. http://pro-audio.musiciansfriend.com/pro...mp;src=3AGGWXX2

Small behringer mixer is pretty inexpensive and more versatile. http://pro-audio.musiciansfriend.com/product/Behringer-Xenyx-802?sku=631263

Many of us like the VTB-1 tube pre http://pro-audio.musiciansfriend.com/product/Studio-Projects-VTB1-Tube-Blend-Mic-Preamp?sku=180360

Any of these will get the mic signal to a line level for connecting to the 'line in' of your soundcard.
You'll also likely find better prices elswhere, but thatsite is a handy lookup site..

Then, as mentioned above, open your BiaB project in RB and start recording on any available track. Just right click the track and make it an audio track before recording..

I do not work here, but the benefits are still awesome
Make your sound your own!