Which map?
That tuto is to install an .img in Mapsource by Gmaptool, nothing to do with Basecamp.
To look at a map in Basecamp, copy the .img in an sd in a Garmin folder,plug it to your pc and start Basecamp.
All the maps( not Bluecharts) to be visible in Basecamp must have MS flag set to 0. [Only registered and activated users can see links. ]
Current Gmaptool version is
[Only registered and activated users can see links. ]

Basecamp is not suitable for Bluecharts, use Homeport instead.
[Only registered and activated users can see links. ]
Bluecharts will show in plotters if unlocked and simply copied in sd in a Garmin folder: one per sd.


Read please our [Only registered and activated users can see links. ]
Most of the matters got exhaustive replies in these threads:
[Only registered and activated users can see links. ]