It's nice and easy to update the details of one of your staff members.
Firstly, you need to be logged into the owner level account, this will be the account that originally signed up to Clara.
Then go to Settings > Organisation > Staff:
From here, you can find the staff member in the list. Clicking on them will take you to the edit screen and allow you to edit all of their details:
Once corrected, click Save at the bottom.