At the Company level, you can set mileage rates based on the IRS published rates. This takes the annual administrative work out of the end users hands and places it in the admin's.
IRS published rates: https://www.irs.gov/tax-professionals/standard-mileage-rates
and under "LOGBOOK TRIP RATE (EG. 0.58)" change the value to the correct rate.
Alternatively you can just login to the Hub and use the left hand nav to navigate there from SETTINGS > COMPANY (as shown below)