1. To make changes to your Yo-Me please go to the option Edit My Avatar, on the top of your player's page.
2. When you access this feature you are able to make changes to your Yo-Me facial feature, background, add pets, etc.
3. Once you have made all the changes that your heart desires, press Save. The changes will be updated after you select which of the Yo-me you would like to be your public Yo-me. Normally, it takes up to 48 hours for the update to take place online.
If you want to use a personal picture from your computer on your profile, you can learn how to do it here.