Without the need to know any of the technical details you can simply write your text and then format it any way you like.
When you first publish your Kindle Book through the KDP Bookshelf, you need to enter a Description in the first step of the publishing process. The Description can be up to 4000 characters long (including any formatting codes) and Amazon only allows certain formatting options (i.e. specific HTML Tags). You do not need to worry about that, the KDP Bookshelf Editor mode of the Amazon Sales Page Tool gives you only the formatting options that are valid here.
After you have successfully published your Kindle Book on Amazon, you can either continue to edit the Description in the KDP Bookshelf, or choose to use Author Central to do so. In Author Central, you also can edit other parts of your books Amazon Sales Page, for example Editorial Reviews, From the Author, Inside Flap, Back Cover and About the Author (not to be confused with your Author Bio).
In these sections, you can use many more formatting options, including Images.
Before you begin to use the Author Central Editor, be aware that editing your Book Description Through Author Central locks you out of doing it in KDP!
You will only be able to edit your Book Description through Author Central and be limited to 2400 Characters (including any formatting codes). On the other hand, you will have more freedom in designing your Book Description. Make your choice carefully.