I did this to my Empulse, I bought it from Germany and live in the UK. It's some time ago now. I'm a bit vauge on it however.
Make a note of odometer reading.
Put the bike on charge, then press and hold the mode and trip buttons for 2 seconds to go into 'setup mode', ( normally used to set the clock) then press the grey 'start' button on the right handlebar for 2 -3 seconds. Exit setup mode and check odometer.
If this fails, report back and I will do it on mine. Reluctant at the moment.
A Brammo dealer would have used the software connected to the bike.