Under the text box on the right, click Go Advanced.
A new text box will open for you to input your text.
Scroll down to Manage Attachments and click on that. A separate window should open.
In the upper right of this separate window click on Add Files.
Click Browse in the upper right.
Navigate to the picture file on your computer and click on that.
Now click on Open and that box will close.
Click on Upload.