The obvious question is have you contacted the seller? Can you post some pictures maybe that would help some money figure out how to connect it.
I just checked by doing a search and found a YouTube video on how to connect the Datex2:
Buy the DATEx2 device here - https://bit.ly/BGBDATEx2Meet the DATEx2 eBike parallel battery safety device.The DATEx2 device allows you to safely connect more...
The video talks about the advantages to using the device, but not the connections. For that I followed the link in the video description to the Datex II Site. The connection are simple, the two outside xt60s are for the batteries, the connection to the bike/controller in the connector in the middle next to battery connector on the left holding the device with connectors facing up. Check the attached diagram.