How do I tag an mp3 file for audiobooks

I use my Clip+ to download and listen to audiobooks from the Overdrive libraray. Periodically some of the books will download properly but when I transfer them to the player (using a Mac) they get placed in the Music/Audiobooks/Unknown file. Today I downloaded 2 books and they both ended up there with the files alternating.

I tried renaming the files with 01 sequence but it had no effect. I tried moving the book folder to Podcasts, no change. I have tried moving the book folder out of Audiobooks entirely, no change. I check the files in Finder and as far as I can tell they all have the same information, so I don’t understand where or what tagging info I am looking for. Is it available in Finder? In Get Info?

I have searched the forums for an answer to this question and all of the answers seem to lead back to “retag the files.” I honestly don’t know what this entails or how to do it. All of the answers presume a familiarity with the process which I do not have.

Can someone please provide an Idiot’s Guide to doing this? Picture me a toddler who is given the keys to the car and told to put air in the tires - Step one, Open the car door, step two, put the key in the ignition. What’s an ignition? I ask.

Many Thanks, and please no snide remarks, I have been using computers for 20 years and am on my 5th player, own an ipad and an iphone and know how to use them so don’t presume I am a complete idiot.