Files not being added/shown in library

[Mart Z. <mar...@gm...>]

Hello,
I'm just getting to know cmus on my xubuntu. Haven't gotten too far
though: as I try to add directories to my library, nothing happens. No
tracks are added; I can't even see any mp3 files during manual
browsing (view 5).

In other words, the physical mp3-files that are nicely to see in
Thunar, just aren't there in cmus. Their folders appear empty.
What could be the case?
Is there a way to manually configure the library, inside a configuration file?

PS, I'm all new to linux/ubuntu as well, hmm.

Cheers & thanks,
Mart,
from Estonia