Alternative Software Application?

Need help accessing maps on SD Card

Garmin ETrex Vista HCx

I have used Basecamp to put a topographical map onto an 8GB SD Card.
It is formatted Fat32 and Windows sees it just fine.
Basecamp said the map was successfully compiled and when I look at the properties it is "not lockable" so it's not locked or something.

When I turn on the GPS it still just has the stock un detailed map of my area. If I go into settings and look at card properties it just shows everything as 0, 0% avail, 0% used etc.

I feel like I am missing something here and this thing is making me feel silly.

The SD Card has a folder named "Garmin" and there is a gmapsprom.img file on it as I was told to expect.

Any help is appreciated!