The information you should know is here: https://en.opensuse.org/SDB%3ABasics_of_partitions,_filesystems,_mount_points
Specialy in your case is the fact that you should know for what usage you creted that partition. Thus when it is for the benifit of one user, you could mount it somewhere inside that user’s home directory (and then of coourse the mount point must either be created by the user himself, or created by root and made owned by the users afterwards. In any case Thcreation of the fstab entry must be done by root. (and using YaST > System > partitioner is a good way to do it.
When you have still no idea where to mount, you could use Fraser-Bell’s suggestion. It could be done like this (but alot of different solutions are possible):
YaST > System > Partitioner. select that partition and edit; Do NOT format it again (you did that already), but choose a mount point, I suggest /mnt/backup and finish that.
Then chheck if the partition is mounted with
mount | grep /mnt/backup
When this gives no line with information, first come back here for more help.
Then, assuming that the username of the end-user is terry, as root:
cd /mnt/backup
mkdir terrybackup
chown terry:users terrybackup
Now, as use terry you should be able to use /mnt/back/mntbackup for creating files ,etc. in it.
To make it more easy terry could create a symbolic link inside his home directory
ln -s /mnt/backup/terrybackup backup
And then you will see a directory naed backup in Dolphin (well, in Dolphin I guess you would call it a map) for terry’s use.
BTW, asking for help with no CLI is not very usefull. All of us can show you exactly what to do in the CLI (often copy/paste is possible), but describing what you should do in a GUI is a nightmare