Hi Peter and welcome to the forums!
The previous suggestions linked to posts and topics regarding the Windows version of Mp3tag. From the screenshot it looks like you're using Mp3tag for Mac and I've moved the topic to the #mac category of the forums 
Regarding your question: to import metadata from the folder structure, you can use Convert → Filename - Tag and denote folders using the / folder separator. I've written about that in Documentation → Import Tags from Files.