I assume you've done all the initial configuration and have at least one page template. It comes with a default template, but it's pretty bland.
build all - rebuilds all existing pages with galleries set to used or holding.
build all with new - rebuilds all existing pages using galleries set to approved, then used or holding as needed to fill the page.
pending galleries will not be used until they are approved.
The included documentation is pretty comprehensive. It covers the commands and available database variables quite well. There is a user run support forum as well
http://forums.unofficialjmbsupport.com/index.php