I've just started using MusicBee9
I'm assuming that's a typo. The latest version of MusicBee is 3.4.something.
Dragging from Explorer into MusicBee should work (even without Ctrl key), but you can also use File > Scan Folders for New Files...
The Navigation Panel
is usually on the left and shows the different parts of your Library and optionally the folders on your computer.
If you don't see that, select View > Arrange Panels...
and add it to one of the available areas and configure it from there.
Bee excellent to each other...