The WWW_CANDIDATE role is a business role which grants access to the Candidate Self Service module, it does not grant execution rights.
The WWW_CANDIDATE web role is tied to the CSS_SPLASH which will display all of the Candidate related self service functions the user has execution rights to.
The WWW_CANDIDATE role should be set up for 1 user only. That user may be granted execution rights to the procedure NEW CANDIDATE either through IMPC or IMUS. The user should also have execution rights to each step on the procedure.