If your LSB is a Trek dealer and the computer you are looking at is a Bontrager, let them install it. My wife got one for her bike for me to install and the instruction totally suck.
The instruction booklet included with the Bontrager computers is very limited. Here is a link to the Bontrager Web site where you can download the complete owner's manual for the various computers. These owner's manuals are much more detailed and will probably answer any installation or configuration question you have:
http://bontrager.com/support/owners_manuals