VS-20

The VS-20 form is a sworn statement that you are authorized to receive a copy of the birth certificate once it's amended. This form must be notarized by a California-licensed Notary Public before it's sent to the CDPH. You can learn more about that on the next page.
Above Applicant's Printed Name, write your new legal name (the one you want to change to).
Under Registrant, write your new legal name (the one you want to change to).
Under Applicant's Relationship to Registrant, write "Self".
Leave everything else blank. You will need to complete the rest in the presence of a Notary Public.
Example
Here's what your form should look like once it's finished (Everything I added is in red for emphasis. Use black when you're filling your form out):