Welcome to MobileRead. The Kindle is almost idiot-proof. You can get fancy with it -- and someone has even written a book to tell you about all the extras -- but if you only use it for reading, it's not difficult to master at all.
To make it easy to download books from this site, turn on the antenna, and from the main menu open the experimental browser. Then go to this url -->
https://www.mobileread.com/mobiguide <-- to grab a copy of the MobileRead Download Guide. After it has transferred to your Kindle, you can use it to browse the library of available books and download directly into the Kindle.
MobileRead owes a debt of thanks to Hadrien at Feedbooks who created the first download guide for his site. You can download it to your Kindle from -->
http://www.feedbooks.com/kindleguide <--. And, if these directions are confusing, Hadrien has posted a video tutorial on his help page for Kindle users. Check it out with your browser at
http://www.feedbooks.com/help/kindle