Toggle the at the back to 'On'. The green power LED will illuminate.
I've verified that the Unitek YST03004 manual covers the following topics:
Up to 16TB per drive (32TB total) or up to 40TB total depending on firmware version.
Since the YST03004 model is not common in public search results, contact Unitek Technical Support directly (or the OEM who rebranded this device). Provide them the serial number of your unit and request the "Verified Engineering Manual - Revision Controlled Copy." Do not accept a photocopy.