You get an “About Blog” widget that gives you the option to upload a portrait photo and to write a brief introduction of yourself.
In your admin, go to Appearance >> Widgets
Drag an About Blog widget into the sidebar of your choice (I recommend the Blog, Left, or Right Sidebar). Please note that if you are using this in the blog area of your website, then you would choose the Blog Sidebar position.
Now you can fill out the information and using the image upload, you can add your portrait to the widget. If you decide to add a signature (an image based one), you can use the other setting to do that.
Click Save on your widget and you are done!