You could do this if you wanted. Due to the amount of words plus limited ability in formatting, we highly recommend using a Word Processing program. A couple of suggestions are Microsoft Word or Google Docs.
Be sure to setup the margins in your file if working with a word processing program.
Then save your book as normal, then click file (in MS Word), then click Save as and then change the file type to PDF.
One you have wrote your book, you should of course save it with the default file type. Then you click save as and choose save as a PDF.
Please see this article about converting a PDF or .doc file to .epub or .kpf format.
You could do the cover in Book Bolt. Create a new project, pick custom, pick 6 x 9 and one page. Then you create your front cover (no front and back cover in ebook).
Then click file in the Book Bolt Studio and pick export to PNG. You will need to convert that .png file to .jpg, just open it in a graphics program, even Microsoft Paint and click file and save as and pick jpg as the type. Or use good to search png to jpg converter. Upload that jpg as the cover.