Log in to your Race Space account using the email address associated with the entry.
Select My Entries from the main menu.
Select Entry Actions next to the entry you want to change.
Select Edit Entry.
A panel opens where you can edit the details attached to your entry.
If a field you need is not showing
Not everything is displayed by default. Select more at the bottom right of the panel to reveal the rest of the editable fields.
The name on the ticket is the exception
You cannot change it yourself. Name changes have to go through the event organiser, so contact them directly. There is a separate article on how to reach the organiser of your event.
This also applies if you are trying to pass your place to somebody else. That is a transfer rather than an edit, and it is covered separately.