How to import cover-art from a file?

OK I feel I must be dumb, but I can't manage to do this. I have a album which no db has the cover, but I have a copy in a file called folder. I can select the tracks I want to add the cover to and then right-clcik on the empty cover icon. I select Add cover and find and select it. The cover appears in the cover window. However if I reselcet any of the tracks, the cover is empty again.

Help please - what am I doing wrong, or what is the way to do this?

Whenever you edit tags in the Tag Panel, you must click "Save" (:mt_save:) to write changes to the selected files.

Oh - yes I was THAT dumb. Thank you.Now I can sort out
the remaing ones with no cover image where I have one already..

Ifyou have just one picture file in each folder or a file with a specific name, then you can import all the covers in one go with the action
Import cover from file
and the respective filename (and even variables and wildcards are allowed)