I can't obviously see how to do this so am assuming you can't. Absolute must for me in the UK. KM are double dutch to me!!
Edwina, you can get miles by changing units in the user interface:
App Settings -> user Interface -> Units -> British
I hope this will help you.
You can change in settings, scroll down to UI settings, there you can select the language and units to be used in the app.
Thanks for letting me.know where that setting was. That wasn't an obvious place. It would be good to have some kind of getting started guide or easily accessible info on the app and settings. You can't search the forums for specific topics ao very hard to find any user info.