The ZCell BMS needs to be connected to the one or more batteries in your ZCell system using an RS485 cable.
If you don't already have an RS485 cable attached to your ZCell BMS, its very easy to make one.
The simplest way is to start with a standard RJ45 ethernet patch cable, and cut off one end of it to expose the twisted pairs inside.
Using the standard colour coding in ethernet patch leads, all you need to do is to strip three wires and attach them to the RS485 port on the BMS using a screwdriver, as follows:
Connect A/+ to the (solid) Blue wire
Connect B/- to the White/Blue wire
Connect Gnd (Ground) to the Orange wire
Then the RJ45 'end' of the cable just gets plugged into one of the Comms ports on the ZCell enclosure (these are wired, internally, to the 'Comms' ports on the ZBM inside).
Note that the latest version of the ZCell BMS has a different pin arrangement in terms of the screw terminals (there is more stuff in there!) - but - the labelling is consistent, so just connect to terminals based on the labelling on the front of whichever version you have.
If you have more than one ZCell in your system, you simply 'daisy chain' the additional batteries onto the first one with standard 'ethernet' patch leads. Note that these are NOT ethernet signal cables, though - they're RS485 MODBUS - so please don't connect a ZCell battery RJ45 socket directly to an ethernet network - it... won't work.