Here's how you can update your first name, last name, and social security number:
After logging in, navigate to Myself>Personal Profile.
In the Demographic Information box, you will see a Name and SSN section. Clicking edit here will allow you to update the text listed in the Salutation, First Name, Middle Name, Last Name, Suffix, Preferred Name, Social Security Number (click "I Need to Retrieve this SSN for Official Business Purposes"), and birthdate fields.
Once your chance is made, click the Save button at the bottom of the page to save it.