1) Create Expense Type with Category Mileage by going to Masters-> Expense Type. On the create screen Make sure in the alternate amount label field you assign “Distance” and for the alternate rate label field you assign “Mileage Rate”. This will add these two fields on the “Add Expense” screen when the user selects this Expense type
Please refer to this blog for steps to create/edit the Expense Type:
2) Then make sure you add Mileage Rate on each user profile by going to “Add/View Mileage Rate”. The Mileage Rate is added to the user profile for a year. Going forward for each year they get added automatically for the next year - we do this via an automated script at the end of each year. The rate has to be added in dollars - for example, if the rate is 59 cents, you will add 0.59
Click here to know more about how to add/update the mileage rate.