Uploading and using my own audio?

I've made a few attempts to upload MP3s to Roll20 so that I'm not limited to the stock effects from Tabletop audio, Battlebards etc.  I haven't yet been able to get a single file to upload properly.   Is this a feature that requires a Pro account?  If not, is there somewhere I can look for guidance on this?  All the information I can find on the forums just talks about using the audio that's already built into the platform.   Thanks for any help/insight. 

Free and Plus can both upload files, I think the max file size is 10mb for Plus. How big are the files you're trying to upload? What kind of error are you getting?

Thanks for the reply.  I'm using a Plus account, although you say that shouldn't be a problem.   After your reply, I started fiddling with it again, and I got it working.  I think I was previously trying to upload audio in the wrong place - in the same way I'd upload pictures.   Anyway - I'm good now.  Thanks for your help.