When will Elsa and Anna be included among the other Disney Princesses? And how do I add an avatar?

Probably 8-14 months after. Jus like Brave. Rumour is that it's in October. Which makes sense, it's a year after the movie. And to change your avator:

1. Go to your profile
2.Do you see those photos next to your profile? Underneath it, in tiny letters is written View more photos. click it.
3. Click Upload new photo. Once you've done uploaded a new photo, go back to viewing more photos. Choose the photo that you want as your avatar by clicking the first icon underneath it. It should be a person with short blue hair and a t-shirt. Once you click that icon, your avatar should be changed.