Welcome C1802362,

There are more than a few trumpet players here on the forums to help you along. A couple that come to mind are Mac, and Matt Finley. They really know this program and you can see many posts by them. I also make my living using my Trumpet and Band in a Box. I use BIAB to make my sequences for performance, as well as practice and for my students. First, you might want to get real comfortable just entering the various jazz chords. The best way to do this is to open the help menu, go to "Chord List", print that list out, and then tape it next to your computer/piano so you can reference it whenever its needed.
Next, I can't recommend enough that you learn to use the shortcut keys to enter chords, this will save you a lot of time.

To answer your question on transposition, after opening the notation window, you need to go into the options menu (Upper left hand corner next to the little 8th note.) From the "Lead Sheet Options" menu, Choose "Notation Options". Right in the middle you will see "Transpose Options". Use the pull down menu to select "Trumpet +2".

Here are a few tips about how I use BIAB for Jazz practice.

1. First, Make a folder on your Desktop called "BIAB jazz practice". All of your various jazz exercises and tunes should be available to you there, nice and fast.
2. Create a new folder in the jazz practice folder called "Scale practice". (Or "Solos", iim7-V7-IM7, or whatever your goals are.)
3. Open BIAB, choose your style, tempo, key and number of choruses. Then type in your chords, using shortcut keys wherever possible.
4. Now, listen to your song, make sure it sounds and looks correct, make corrections, name and save the file in the folder of your choice.
5. Practice your scales, or patterns at a slow tempo with lot's of repetitions. For example, If I'm going to work on my major 7 Be Bop scales, I will type my progression>Bar1 CMaj7 (CJ), Bar2 Dm7/G. then I copy those 2 bars a few times, then set the chorus to repeat 25 times after bar 8. I end up playing those scales 100 times very slow. That's on Monday, on Tuesday I open the saved file, and then transpose it to F, Wendsday is Bb, etc. There are endless variations. Make sure you experiment with different stlyes.

Now, here is where it gets good>
I find that the Soloist is one of the coolest things about BIAB. So when I want to get some good ideas going over a new set of chord changes, I will do all the above until number 4. Next, I do the following>
1. Make sure you have a 4 to 8 bar chord progression to start with.
2. After you have your progression, open the soloist and choose>Pat Martino 16th soloist. I don't know how it was put together, but the lines that come out of this soloist are AMAZING. And I can promise you a good hard harmonic workout in playing these lines.
2. Now open the Notation window (Not the Leadsheet window!)
3. Click on "S" to see the soloist (You should change the transposition and octaves in the Leadsheet options as above)
4. Listen to the solo, when you hear a lick or pattern that you like, click "LoopScn". This loops the current bars so you can hear the line over and over.
5. I then slow it down to 50, and work that line for a least an hour a day. I gradually will increase the tempo until I can play that line at tempo with no errors or hesitation. In fact, I will right click and mute the solo part to make sure I sound good. Since you saved the file, you can open it everyday at the new tempo, and then start to work on the next pattern or lick.

I have collected a ton of pattern and lick books, which I make into folders of tunes. I then play in the exercise using my midi keyboard. Depending on if I want sight reading or pattern/scale practice, I will open 1 folder a day in the Jukebox, and let er rip! It's good because I never know what's coming next. This is also great for learning/playing/transposing Tunes, I now have over 17,000 BIAB files.

Good luck, sorry for the long post, hope this helps someone, PM me if you need more info,
Ed