A client can edit any of the details found on their profile.
To edit your profile photo - click the blue edit icon on the bottom-right side of the photo.
To edit any of your other account info - click the white button labeled "Edit" in the top-right corner of the Intro Box. That will open an "Edit" pop-up where you can modify any of the following:
The client's username
Email associated with the account
Phone number
Country and State
For instructions on how to edit your payment details, see these articles: