WordPress.org

1. Create a new directory in /wp-content/plugins/ called yamm.
2. Upload yet-another-multi-site-manager.php & yamm-signup.php into the directory you just created
3. Upload sunrise.php to /wp-content/. If there already is a sunrise.php file there you will have to merge the two files.
4. Edit wp-config.php and uncomment the SUNRISE definition line: define( 'SUNRISE', 'on' );
5. As the site admin activate the plugin through the 'Plugins' menu in WordPress MU.
6. Go to 'Site Admin->Yet Another Multi-Site Manager' and add domain names/change the signup page slug.

NOTE: If you are using the WordPress MU Domain Mapping plugin, use dm-sunrise.php instead. You will have to rename it sunrise.php once you have moved it to /wp-content/.