Not being able to add metadata to WAV files has been a continual frustration. Until now. Apologies if this is already common knowledge but it’s new to me, so I presume it will be for others.
Download Audacity, which is free. Drag and drop your audio file onto Audacity main page, go to Edit > Metadata and add info. Then, File > Export > WAV. Job done. According to the discussion I read online, the file used needs to be at 44.1kHz/16 bit to work transparently, which is fine for radio.