Which country would you like? Each country has its own clon of openstreetmap, those usually have some added value, i.e. in my country it has marked trails by color according national turistic marking, so I would propose to google such for your country. Usually it contains also manual how to install- both ways proposed above work. General openstreetmaps are here: http://garmin.openstreetmap.nl/ for the world.
Thanks. img files I can copy into the Garmin folder „maps“ but basecamp cannot find it. The openstreetmap gives a map file. This I can open but it does not include any topographical information. Any experience with .img files?
The img-file has to copied directly in the Garmin-Folder of the watch (and not in a subfolder below Garmin/). Usually you shoud have in this folder more img-files!
In some case, topo-Maps are not activated for base-Camp. In this case, you could use the small programm IMGname, download from http://www.javawa.nl/imgname_en.html. With the program you can set "visible (or not) in BaseCamp"
In February I visted arvidsjaur in North-Sweden and used OSM-Maps
