I used someone else’s email address to sign up for Facebook.

Have this person assist you in accessing the account. Once you have done this, update your login email address information by taking the following steps:

1. Go to the Account Settings page.
2. In the "Email" section, carefully type your alternate address.
3. Click "Change Contact Email." An email will be sent to this address containing a confirmation link.
4. Click the link in the email to complete the process.
5. You can then add your personal email address from this page and remove the one that does not belong to you.