You may have had another user designate you as a proxy applicant for them. Being a proxy gives you permission to submit applications on behalf of another user (only for applications and no other actions).
Steps to Submit Applications as a Proxy
1. Make sure you are logged in to the system (use the "Login" link in the upper right corner). Then go to the opportunity. You will most likely access this from the homepage of the site, or via a direct link.
2. Click the Apply as Proxy button from the local menu on the right side of the screen.
3. From the dropdown in the proxy section, select the name of the applicant for whom you are submitting an application.
4. Fill out the application form as you normally would.
5. Save or submit the application as needed.
6. You will see confirmation of the submission on the screen and the applicant (the person you are applying on behalf of) will receive email confirmation of the submission.