All active candidates at your test center are listed in Candidates.
You can filter the list by typing the first letters in a name or the ID.
You select candidates by ticking the box on the left. When you tick the top box, all candidates will be selected.
Click Deactivate selected to remove candidates. You will have to confirm your action.
You can also merge two users if the same candidate has been created twice. Click in the box to the left of the candidates and click on Merge candidates.
A popup will appear and show you the different users and their test history. Underneath the warning message personal details are shown for both users. You have to choose which of the users you want to keep. When you've done that you can click Merge candidates in the bottom of the popup.
Create candidate is described in a seperate article.