To get started, go here
The Mobipocket creator "publishers edition" is the option you want. It will convert your files to a PRC document which Kindle uses. You can also download the reader so you can review the files after you convert them.
After you download Mobipocket you can build the prc file with the following steps:
1). Open mobipocket
2). Under the heading "Import from an existing file" click on the format that your original file is in (Example: Word).
3). Click the browse button and find your file.
4). Enter your file and click Import.
5). Once your file is imported click on the left mouse button "once" then click the build button at the top of the page.
This is just one of the many handy tips and strategies you'll discover in my "Insider Secrets to Self-Publishing Your Masterpiece Course"