I have Garmin Topo 100K maps on DVD and I installed pretty much entire North-East onto my GPS some time ago but hopefully I still remember the steps:
- I installed Basecamp on my computer
- I ran installation program from Topo 100K DVD that copied that maps to my computer
- Once I have done this I was able to select Topo 100K in BaseCamp via Maps menu
- To select & transfer map segments to my GPS I attached it to the computer, started BaseCamp and then selected Maps -> Install Maps and followed fairly
obvious steps.
Having said this, let me also opine that Garmin Top 100K are good for contour lines only and the street data seems really old in the version that I have (like it wasn't updated since the 50's in many locations)
I am a big fan of
https://www.openstreetmap.org/ for trails & parking areas (I switch between OSM & Topo 100K when I need to view terrain), and luckily Garmin keeps their maps format open enough that it is possible for people to create OSM version for most (newer) Garmin models. You can read a lot of details at
http://wiki.openstreetmap.org/wiki/OSM_Map_On_Garmin/Download however, for simple needs it boils down to 3 simple steps:
- Select U.S. region of interest and download it from http://daveh.dev.openstreetmap.org/garmin/Lambertus/latest/kml/kml.html - this is updated weekly
- Copy map file to your device (or memory card) to /Garmin folder
- Enable display of OSM map via Maps settings -> Select Map (exact menu sequence varies by model.)