how to rename files on SD card

I always struggle to rename files in OSX in the finder. This morning, I need to rename some .mp3 files I made last night; they're live recordings of songs I want to rename before importing them. Nothing I do seems to highlight the file name so I can rename it. I've hit ENTER, nothing happens, I right click, no RENAME option appears, I click and hover, nothing happens - every technique I find in a Google search for file renaming does nothing. I"m using OS 10.10.5, any suggestions?

Gary