The Bio Widget showcases you! Choose wether to upload a portrait or not.
When you choose to upload one, you can either upload a file from your computer (through the regular WordPress Media Library) or pick your WordPress avatar, which can be defined in Users.
If you’re familiar with Gravatar, your WordPress avatar may already have been defined, based on your email address.
Avatars have a defined size of 75x75px.
There’s also a Read More → link, that could point to an About page you may have previously created, or any other profile. Simply customize the URL field.