hmmm well looks like you dont have FSD which is why you dont see the beta option. To clear up any confusion...
-- "Full self-driving computer" refers to HW3, the on=board computer required for FSD beta (which you have, as do all Teslas built from toughly mid-2019).
-- You can buy FSD today, but this will only get you the currently available FSD components: Smart Summon, NoA with auto lane change etc. Doesn't look like you have this.
-- If you have both of the above, you should see the option to enroll in the FSD beta, which is testing the "city streets" version of FSD.