This will get you started on kits.
As far as the blue ticking goes, if you already had the kit, it won’t have disappeared. Just make sure the check box in front of the kit’s name is checked in the drum kit list. If the kit appears to be disconnected from a song, just reselect the kit as the default kit for that song.
When you open a kit to look at it, BBM thinks you changed it. This may mean you then need to reselect the kit for your songs. This is one of the many bugs that have never been fixed.