In the left side menu in the GUI: Under Storage, Disks, find your new drive , select it and wipe it, with the wipe button. (DON"T WIPE AN EXISTING DRIVE.)
Then go to Storage, File Systems and click the Create button.
A dialog box pops up: In the Device line, select your wiped drive. On the Label line give the drive a short name. Then, select a format type on the File System line. If you're note sure, EXT4 is probably the best choice.
To use the drive:
For creating shared folders, network shares and other tasks, take a look as this -> Guide. You might find it useful for some of the things you may want to do.
Good backup takes the "drama" out of computing
Primary: OMV 3.0.99, ThinkServer TS140, 12GB ECC, 32GB USB boot, 4TB+4TB zmirror, 3TB client backup.
Backup: OMV 4.1.9, Acer RC-111, 4GB, 32GB USB boot, 3TB+3TB zmirror, 4TB Rsync'ed disk
2nd Data Backup: OMV 3.0.99, R-PI 2B, 16GB boot, 4TB WD USB MyPassport - direct connect (no hub)