You have to start a 360 page. Since Yahoo will be switching soon, check out Multiply.com or check out Mash.
To start a 360 page, go to your profile and click Edit Info
It will ask if you want to start a 360. Click on it.
Fill in the necessary information and begin your page.
Go to my page and where the picture goes, in the left hand upper corner, you will see Edit Personal Photos.
Click on that and you will see where you can upload photos from your computer.
When you’ve done that, choose the picture that you wish to appear and click on Use As Primary on the right side of the page.
Scroll down and click on Save.
Go back to Edit info on your profile page and click on Use 360 image.
You should then have the avatar of your choice