EVERYONE is a beginner at one time or another. smile
Yes.... I remember when I first started with BIAB. I never thought I'd ever manage to get the hang of it. Then I got Sonar (a DAW by CakeWalk) and I had to go through another learning curve.
Moving from Sonar to Reaper was not to bad because I had some understanding under the hood!
So to answer you question...
What I do is to create a song in BIAB.
I then save each of the tracks as WAV files and take them to Reaper. Prior to saving the tracks, though, I set the mix to "Flat, Dry and Center" -- this is an option that's found by right-clicking on the "Master" track.
NOTE: "Flat, Dry and Center" means that the track is saved without reverb, without panning and without tone adjustment. I prefer to use plugins in Reaper to do those things.
Once the tracks are in Reaper, I add effects. Then I adjust the volume and create a balanced mix.
User DeaconBlues but the below short tutorial together that might be useful for you.
https://www.youtube.com/watch?v=hUKGWZhJ2vo