Update EHS36 firmware with T46G?

[CeeTee]

I have a number of T46G phones that I'm configuring to use a hosted PBX.

I only have a minimal config on the phones at the moment, just enough to load the network details via DHCP. All other settings are still default, and I'm not auto-provisioning yet.

I have updated the firmware on these phones to 28.73.0.40

I have now been told that the phones each need to use a Plantronics CS510 via a EHS36.

I believe that I need to upgrade the firmware on the EHS36 for this to work properly with the T46G.

This is my first exposure to IP phones (converting from an analogue PBX) let alone Yealink phones, and I am finding it difficult to understand the documentation for the process of upgrading the EHS36 firmware.

Can someone please explain to me (like I'm a 6-yo) why this requires the 'zero-touch' process, how it works, where does the firmware get downloaded from, and what settings the process expect the phone to have for it to 'just work'.