CEL MeshConnect programming

I have a ZM357S-USB-LR, from my reading these devices come without firmware, and require an ISA3 to program them. Which I’m willing to get. But I can’t find any tutorial documenting how to use the ISA3 to code it. And which version of firmware to download and install on the ZM357S which works with openHAB. Can anyone help me out?

Okay, got the Simplicity Studio installed, and managed to download the em3xx_load utility, which will write firmware via USB(?) negating the need of the ISA3? But I still have no idea what firmware or where to download it.

How did you get this done? Did you follow some documentation?