I don't mean to be a smart ass but why did you buy a system designed for use by people who know how to make maps from scratch? you're asking us so that must mean you don't know how. these things are for competition use by professional race teams. not meant for the average consumer. there are better systems available for that.
maybe someone on here has one for you but I highly doubt it. it doesn't make sense to use a "base map" if you're serious enough to invest in these systems.