I did the exercise today on my GPSmap 176C for the same files and I got great help:
Step 1. Create a directory c:\Garmin.
Step 2. Unpack the .rar files in the directory c:\Garmin
Step 3. Run the install.bat file.

Now, open MapSource.
Strangely enough, for me as a beginner, after step 3 the map showed up in MapSource under the File button.

Hope this will work for you too.