Mount the SSD drive inside the USB case then connect the case to the Orange Pi Zero. Connect a USB-to-Serial to the Serial Header on Orange Pi Zero board.
2
Acquire some knowledge
Watch a tutorial on how to do a file server with Raspberry PI3 to get aware of the steps necessary to implement on the Orange PI, which are basically:
Without getting into much details (there are good tutorials online) the following steps are necessary:
Download Armbian and write the image to the Micro SD card.
Using a terminal program like Putty (windows) or Screen (Linux) check that the machine is booting.
On the serial terminal setup the wireless network to be able to access the machine later without the serial adapter using SSH.
Install and configure DHCP server (link with good explanation)
Format the SSD drive. I have used ext4 as a filesystem to be able to use iso images larger than 4GB. Some tutorials advise to install NTFS (ntfs-3g) support for Linux.
Make SSD drive mountable on system startup (linkwith good explanation)
Install and configure SAMBA Server
Check that it is possible to accesse the file share from another computer