Xiaomi M365 Edition Owner's Manual page 20

INSTALLATION - CONNECTIONS - HANDLEBAR CONTROL UNIT
The connection to the Handlebar Control Unit is made via a 6 pin
connector.
Inspect the interior of the connectors before plug them in. The pins inside
the male connector are fragile and can bend if both connectors are offset.
There's also an arrow icon on each connector's enclosure. Aligning both
arrows will ensure you the connection can be made.
Once both arrows are aligned, apply some pressure to secure the
connection.
You might be left with some extra handlebar control cable. This leftover
can be coiled inside the head tube, underneath the ECU.