You install it as you would any mod without an installer:
1. download it
2. move the .rar archive to the \modules\ directory in your M&B directory
3. right click on the archive and select "extract here"
4. launch M&B, and in the dialog box select "customizable troops" instead of "native"
5. as soon as you enter Zendar, go to the 1st floor of the tavern to get a special blessing