While you may be able to do it online ( https://www.ssa.gov/applyforbenefits/ ), I would suggest you do it in person at a social security office. However, the field offices are generally still closed due to Covid - please check this page to see your local office will be open: https://secure.ssa.gov/ICON/main.jsp .
Whether you can do it in person or online, you should look for the following information to "prove" you are you, and that you were married and divorced from your ex:
- Birth certificate or other proof of birth;
- Proof of U.S. citizenship or lawful alien status;
- W-2 forms(s) and/or self-employment tax returns for last year.
- Final divorce decree, if applying as a divorced spouse; and
- Marriage certificate.
For more information, review the information found here: https://www.ssa.gov/forms/ssa-2.html