Here's a VIDEO that may help you- Enable Miles editing not allowed in Site Configuration or you can also use the following instructions to solve the issue.
1. Go to "Site Settings" located at the lower end of the left menu.
2. Scroll down on the left menu and click "Site Configuration."
3. Find the "MEMA" rule and checkmark the box to the right of "My Appointments" then scroll down and save at the bottom right and you're done.