Under the Travel Claims section at the top of the screen you can Add New Travel Entry. This journey will then be calculated on the travel claims report giving you an exact amount that can be claimed as a mileage expense.
You also have the option to include a flat rate subsistence claim confirmed by HMRC.
To view a travel claims report:
1) Click Reporting
2) Click Generate Travel Report
3) Enter the Date range you wish to see the journeys travelled
4) The report will be generated, at the bottom of the page will be the total amount to claim in mileage and flat rate subsistence.