All of the upcoming aikido seminars are displayed on the calendar page.
From that page you can click on a seminar to see its full info displayed. From the full info of the seminar look for the gear icon to enter the UPDATE screen.
The seminar info will be displayed in a form. You can update the form as need be to get the correct information for the seminar.
When you save it an activity update will be recorded to the seminar to say that information has been updated.