Create a Sims account.

[Rin]

I got the Sims 3 on Steam and I want to become a member on their website so I can get Simpoints but in order to create an account, I need a Persona but I don't know where to get it. It's a requirement so I can't just skip it. What's a persona and how do I get it when I bought the game on Steam?

[Veonix-E]

You can play just fine without a Sims 3 account. You only need one if you want to access the social features of the game and if you want to buy stuff from the Sims store.

You need an Origin account for the Sims 3 store. If you do want to register, you will recieve a copy of the Sims 3 + whatever expansions you register on Origin as well.

[cruinne]

I believe the Persona is the name you want to be known by on the site. Like here on Steam, I am cruinne.

And, as above, if you already have an Origin account, you should use that to log in at thesims3.com rather than create a new account.