The easiest way would be to download Send to Kindle for PC at:
This application loads onto Windows Explorer.
Use MS Word to maintain your document. You can enter the page breaks, chapter breaks, etc. to create a well formed ebook.
In Windows Explorer, navigate to the folder where the Word doc is located, right-click on the file and choose Send to Kindle.
If you have wifi, in a few minutes your document is on your Kindle!