Go to Amazon http://www.amazon.com/ref=gno_logo
Then >shop by department, >Kindle, >free reading apps
Once downloaded, a Kindle icon should appear on your desktop
Now you are ready to get those free (and purchased ebooks)
This should be the top 100 free list
If your chosen book doesn't show up in your reader, you may have to sync it. That option is in >tools
The cloud reader is nice but any device, other than your pc, needs to be a Google-recognized product (unless there is some way around it that I don't know about).
Pam's Pride blog offers a great service to her readers by recommending free ebooks for homesteaders, preppers and do-it-yourselfers on a daily basis.
Project Guttenburg also offers its readers the choice of Kindle, epub, downloading or just reading online.