Xiaomi M365 Edition Owner's Manual page 9

The Handlebar Control Unit is supplied with a 2 metres cable length and a
Higo connector. The cable runs inside your Xiaomi's stem, along with the
brake line - usually a red cable.
Insert cable inside the stem with the
With the help of a pair of pliers, grab
the cable at the bottom of the stem
brake line
Leave the cable loose until you got the
battery compartment opened.