Here is the website with the petition: https://recallgavin2020.com
It's a little bit complicated since this is a "real" petition for a ballot measure, the kind that people at the grocery store approach you with, so must of us have seen this kind of petition before.
You have to download and print the petition. There is room for 5 signatures on each page, so you sign one line, and hopefully you can get four more people to sign it, too. Only CA registered voters are allowed to sign.
In addition to signing the petition yourself, you will have to fill out and sign the bottom of the form as the one who collected those 5 signatures. Then you mail the form to the address on the bottom of the page. You are allowed to collect and mail in as many signatures as you want, but you can only sign it yourself once.
Let's get rid of him!