It’s pretty simple, really. Go ahead and record your midi drum track. If you want it split up into main loops, fills, etc., each is its own track. The only thing you have to be careful with is that your midi track must end up with drum notes that are in the B.B. drum kit. The biggest issues are that B.B. stock kits have the kick only at midi 36, not 35. Also, they only have 3 toms, normally at 45, 48, and 50. Hi hat articulations are limited to open, closed and pedal.
Once you have your midi files created, create a new song in B.B Manager. Click on the song section in you new blank song where you wish to place a part. Navigate to your midi file and select it. Bam - it is in the song. Just make sure you have kit selected that contains the sounds you want, and you should be good to go.