How do I calculate cost of mileage for mandatory out of town medical appointments (in Ontario)? How does this get entered into the tax program?

Thank you for choosing TurboTax. You will have to manually do the calculations for mileage based on CRA guidelines and enter as "other" on the medical expenses page.

Please see CRA guidelines below for calculating out of town medical appointments:

https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/rc4065/medical-expenses-2016.html#toc14