Choose the format for your e-book and then use a program to convert your manuscript. For example, you can use Adobe software to convert your manuscript into a PDF file. You can also download any number of free converters to do the same if you want your e-book to be in PDF format. Check with an index of free downloads like Softpedia for e-book compilers and converters that will put your work in the chosen format for your e-book.
Decide whether you want to get an International Standard Book Number or ISBN for your e-book. You don't need one if you are simply going to sell your e-book through your website, but one might be required if you plan to sell through other distributors. For example, Amazon doesn't require your e-book to have an ISBN, but Apple does. If you choose to buy ISBNs, you can get them by contacting R.R.Bowker, LLC.
Set up a website to host your e-book if you don't already have one. Unless you are willing to pay for maintaining the website, you should use a free blogging service like Blogger. Some blogging services might charge you for selling through them, so pay close attention to their terms of use.
Set up a payment processing system to handle people ordering copies of your e-book. You could purchase shopping cart software to handle the process, but it'd be both easier and cheaper if you simply used a service like Paypal.
Promote your e-book. Since you have no one else involved in the publishing process, the entire responsibility of promoting your e-book and ensuring that it sells falls in your hands. Since your e-book is hosted online, you should focus your marketing efforts on forums, blogs, and social media sites that focus on relevant topics.