Hi Mark
Just install a MASSOTH Decoder (LS, XLS...) in your LGB Loco and put it on the track and connect the PC Module to the track. Download Massoth Service Tool and start programming.
You may have already a DCC installer installed on your loco. In that event, you don't need to open the loco, by looking at one of the CV (I don't remember the number) you will get the Manufacturing ID directly in the Massoth Service Tool. The detailed instructions for that operation are on the Massoth Web site (in the Wikisite)
Regards
Bruno