Hard drive folders

I have wanted to add some MP3’s to my UnitiStar’s external drive. I note there are three folders LQ/MQ/HQ which I assume are low/medium/high quality. All of my current music sits in MQ - this has been added via UnitiStar copying. I thought if I added the MP3’s direct to the LQ folder (the drive removed from the US and plugged into pc) that would be appropriate. However, none of these appear in the available music list on the Naim app.
Could someone advise please: what is the correct action to make these visible and playable?
Thank you.

Rather than using the LQ folder I would just put the files on a memory stick or SD card and connect that. Then look for it in either the USB input, or preferably the Server input under Local Music.