There are many solutions to this, including one from our web-site called www.trailpeak.com. At Trailpeak you can upload/download GPS data for mountain bike trails (and any others). This is just simple text files (.txt), but if you submit with G7TOWIN format (google it) we will plot the data, so it's a quick and dirty plot/map. You can use G7TOWIN to download other trails from Trailpeak into your unit (if you see it plotted on our site).

Other approaches are to purchase GPS software such as OZI-explorer, or, Touratech, and, then purchase topo maps from a supplier (us) for Canada, or, other for U.S. Then import your topo maps into your GPS software, then, import your GPS data (you may luck out and get a conversion from your GPS software if it supports the format of the GPS data you have -- you can find other converters out there). So, this is desktop solution, whereas the Trailpeak solution is primarily a WAYPOINT exchange

Give it a try, upload your trail, GPS data, pictures, description to Trailpeak, and, over-time you'll see thousands and thousands of new trail info! We're mostly B.C. and Pacific Northwest, but accept GPS data from anywhere!