Step 1:
Add froobskindlebooks@gmail.com to your kindle's Approved Personal Document E-mail List
Step 2:
Have your kindle's email address ready
Step 3:
Login with your email and navigate to the Library page, enter your kindle's email address at the bottom, and download some books!
Press "Sync" in the drop down menu on your kindle to get the new books to show up (takes a min or two)