https://support.sonos.com/en-us/article/add-your-music-library-to-sonos

https://support.sonos.com/en-us/article/no-tracks-from-mac-usb-drive-in-sonos-music-library

Thanks Stanley_4,   Somehow in trying to get the flash drive attached I found that it needed to formatted as Mas OS External, not fat etc.  Once I did that, the folder was attached.   My next task is figure out how to see past the  flash drive folder.  The music folder from the mac has individual folders I created (classical, rock, etc.).  I can click on  a particular folder to see subfolders, then finally individual songs.  Not so with the flash drive.  I must use Sonos folders (artists, albums, composers etc) to find what i want.  I clicked on something when I set the first folder up, sort by folders or something but cant remember how i did that. 

Did you go to “My Sonos” on your controller, open Edit mode and add the Folders category there?

Not sure what you mean.  I had the flash drive folder open on the right of the screen “no selections available.”  Went to the edit drop down box.  My choices were search, start dictation & emoji…  I selected search - and typed name of the folders in search box on the right side above the folder name.  The system found 1 folder.  It was a name of an artists.  As soon as i cleared the search the name disappeared.  i typed the name of the second folder “9 - “  It could not find it.  Guess since it was not the name of an artist, genre etc.  Also, have clicked on/updated library a couple times though there hasn't been any change to flash drive.

Are you doing this in your Sonos controller on on some Mac App?

Not Mac, but on Android:

If you open your Sonos Controller you should be able to select the “My Sonos” section.

From My Sonos you should be able to select “Edit” in the top right corner.

From the Edit screen you should be able to add “Folders” as a selection.

Pressing “Done” in the top right should return you to My Sonos.

Scrolling to the bottom (if you didn’t rearrange the order) you should find your folder menu.

I’m using m

Using Macbook OS Ventura 13.4.  Edit drop-down has the following options:  search, start dictation & emoji…  Today, sonos would only open partially, had to uninstall, download latest version & start over.  I’ve given up trying to see my folders on a flash drive.  I dumped all my music into the music folder residing on the mac.  That way I can see music sorted in folders the way I set them up; as opposed to sonos or itunes.  Stanley thank you for your help and your time.  TLM