Mount drives

If disk is already formatted, You can mount it. You may need to create a file system for it though. 

If you do, Replace XY accordingly, but double check that you are specifying the correct partition

mkfs.ext4 /dev/sdXY

Do that to all the drives/partitions you need to.

Now you should be able to go to "Disk manager" in the GUI or, mount the drive/s manually. 

 

Terminal:

create a mount point (if you haven't already)

sudo mkdir /directr/to/moun/to

Now mount it:

mount /dev/sbxy /new/mounted/location