[Tablet] MicroSD question

Hi Community:

I have a 32GB SD card and put it into my tablet. The tablet saw it immediately and formated it. Nice!

Now, I want to put a bunch of music on it (mp3s and flac files).

I tued the tablet off, and put the sd card in an adapter then plugged it into my Ubuntu tower computer where I store all of my stuff, including music.

I tried to copy stuff from my Ubuntu tower computer to the sd card.... but it is read only!

I tried doing it with sudo also, but it is still read only!

How do I get media onto that card??

Then, how do I play music???

Thanks,
Not so smart Old Jimma from the even older than usual Old Country