First, open the season this class is linked to, and then the class details:

Then, click on 'Edit' and you will be transferred to the following page:

Here you can: update the name of the class, description, change the venue, add a new staff member, colour, start and end date, and price.
Don't forget to save all changes once you finished!

Please note: an archived class's dates cannot be changed. If you have set up an active or upcoming class with past dates, you can copy it, change the dates to correct ones, and delete the one that's archived.