Hi Sam,
This may help you but I don't know what sort of Router you are using.
You first have to set up your Router to allow Band-in-a-Box to "speak" to your computer.
There is a video tutorial here:
Setup Network Your Router may be different (mine was) but if you can follow the instructions it is pretty easy
(the worst part for me was finding out where my Router held the information, I found it under Application Sharing)
You then need to go to your Band-in-a-Box on your computer, select Window and at the bottom is the BB2Go folder selection.
This will open a new Window that will allow you to start the Band-in-a-Box Server.
Once you have set your Server to be on line you can test it with the Iphone,itouch,ipad App.
Go to the Iphone App and select File/Server and there you can connect. If all is well, you will be able to connect to the Server(my App connected without any problems, so if you have trouble you may have to call PG)
NOTE: You have to install the latest version of Apple Quicktime on your Computer to get the ability for Band-in-a-box to create MP4 files (I am talking using a PC here)
Then you can save some songs into the bb2go folder (it resides in your BB folder) then when you use your App on your iphone,itouch,ipad, and you are connected to the Band-in-a-Box Server you can Get the songs.
Now to save some time you can get Band-in-a-Box to generate the MP4 files prior to getting the song.
Just go to your Computers Band-in-a-Box select Window/BB2Go (prepare MP4 Files for the iphone)
In there you will be able to generate the MP4 file for your song/s.
The iphone,itouch,ipad App will now gust download the song (rather than having to generate it, which can take a little while)
Sorry for the long winded reply but there isn't an easy way to describe it..
Hope this helps

Best regards
Michee