Well, you get a Tamagotchi, get a digital camera, turn of the flash and turn on the macro setting, get it in a well-lit place (prefferbly outside during the day), and just take a pic! Then upload it to your computer, then if you want, upload it to the internet using TinyPic, ImageShack, or PhotoBucket.
If your talking about avatars, then this is in the wrong section. To learn about avatars, go here.
u go to settings(at the top of the screen) on the drop down menu it says edit avatar. click on that. that brings u 2 a new page. click on "choose from our own gallery." (or something like that) and choose one