Go to the Administration centre. Then enter the People tab.
Find the person in the People list using the filter tool, add their name to the Specific Employee field and Show Results.
If you can't find the person you're looking for, they are probably deactivated or an external feedback-giver. To check, you can apply the following filters (one at a time). If you need to search for a specific user, put their email address in the Search for text field.
Once you have found the correct person, click on Edit located under the Edit column.
If you get an error saying 'Sorry - [email] already exists', please see the help page.