Help with understanding permissions for folders

I'm rebuilding my Plex media server. I have a single HDD with my first installation of Ubuntu. I'm slowly moving media from an old external drive into folders; Documents, Music, Videos, etc.

I need to give Read/Write permissions to these folders for a group, but the group (media) isn't coming up. I can't make folders anywhere else (e.g. under Computer) using Gnome, and I'm not familiar enough with terminal commands to just try my hand at it.

Can anyone help me figure out either a) how to allow a group to access to these existing folders; or b) how to create a space for my media in another place, please?

I used Nautilus to create a folder inside snap and set it to 777. I'm not sure if that's the best way to accomplish what I want to do, but it worked.

This article should clear things up for the future: https://phoenixnap.com/kb/linux-file-permissions

First, you should check if you actually created the group via:

cat /etc/group | grep "media"

You should get an output like:

groupname:x:groupid:users

In order to give whole group permissions to a file or folder, you need to use chown, but recursive since you don't just want to give the permissions to the folder, but to all the sub-folders and files. So it's:

chown -R :groupname /path/to/folder

Note that sudo might be required if you are not the owner of the folder. You can check the current permissions and the ownership via:

ll /path/to/folder

Hope that helped you, maybe check out the manpage for chown ;)