To update a client you must have the Client manager role.
Users with this role can update a client from the workflow page for the client. The second workflow process is called 'Update client details'. Click on 'Update' in this workflow box. The form to edit the client will then open.
Once you make your changes and save the form, the same workflow steps will apply as when the client was created.
The screenshot below shows where to click to update the client details.
