I have a mp3 folder that I have already downloaded the cover art. I would like to add the cover art to each of the mp3 files in that folder. Is there any way that I can do with without connecting to the internet and changing the files I currently have. I just started using the database function and it is great but I don't want to mess anything up by connecting to the internet and modifying the current files. I hope that you understand what I an trying to do. Thanks in advance.
Yes, you can use an action Import cover from file to mass-add cover art from local files or use the extended tag dialog at
View > Tags...
to add the cover art manually.
Can you mass import covers and filter out the mp3:s that already has a cover embedded, to avoid having double covers in some files?
You can create a new column "Covers" via View > Columns and use %_covers% as value. After that just click on the column header to sort the files by cover count and select only those which doesn't have a cover yet.