If the avatar image was uploaded to your account, you'll be able to find it in your image library, which you can then drag to the tabletop to create a token and set as the character's default token. That said, if you don't have a default token set, dragging the character to the tabletop will create a token with the character's avatar as the image anyway. For bonus points, the token you create in this fashion will already be set to representing the character, so you'll be able to link the bars to the character's attributes, and you'll be able to reference the character's attributes with @{selected|attribute-name} in macros. You can then finish the token setup (for example, linking bars to attributes, setting dynamic lighting range, bar visibility, etc.) and set it as the character's default token.