Sure, it is simple, really.
Here are the steps:
1. Go on www.google.com
2. Click on images
3. Type in the catagory of the avatar that you want, (example, Tamagotchi) and click search. The picture in the right hand corner is called an avatar by the way.
4. Right click on the avatar and select, "Save picture as." You can name it whatever you want, but remember what file name it is under. (Example, My Pictures)
5. On Tama Talk, go to Settings then Edit Avatar.
6. Click on Browse.
7. Type in the name of your avatar. While you are typing it, a box should pop up under where you were typing that says the name of your avatar with .jpg or something else at the end of it. Click on that then click on OK.
8. Click on Update Avatar and CONGRATULATIONS! You have a new avatar!
I recomend you print these directions for further reference! lol
Good luck getting an avatar. If you don't understand anything I just said, just let me know.