The disks will be inaccessible to the host operating system until a RAID or pass through device is configured.  

Download and install ARCSAP controller software.

ArcSAP RAID Configuration Software : Technical Support Portal (freshdesk.com) 

Once installed open the ArcSap utility and verify in the "Recent Tasks" that it is connected.

Expand the "local host" and verify the ARC 1886 is present.  If you see a "Pass Through" device configured, this is for LTO connectivity to the host. 

Right click on ARC-1886 and select "New RaidSet" 

There are multiple instances where ArcSap will request a password.  The default is 0000.

Once the password is entered a scan of available disks will be presented

Select the disks that you want to group together in a RaidSet.   The total capacity will be shown in the upper portion of the screen.

Select the "Create" button once you have selected your disks. 

Now that the disks have been selected as part of a RaidSet you will need to create a volume to present the storage to the operating system.    Exit the RaidSet screen and return to the main page.   Right click on the created RaidSet and select "New Volume".

In the new volume screen you have the option to name your volume and select your Raid Level.  The Raid Level determines the maximum capacity of the volume.   

Once all details are set select "Create" 

Verify that the Raid set and Volume are present.  Once configured the volume will now be presented to your operating system.

under disk utility (macOS) or disk management (Windows) you will see an unformatted volume.  Erase and format within the operating system. 

The RaidSet volume is now ready for use.