Originally answered May 18, 2017
Choose an important topic that encompasses what you have blogged about. Create an outline and sort your existing posts into categories. As you do this, you will revise your categories, which will become the chapters of the book.
Edit the content so that it flows well. Add any missing content needed to complete the chapters. Ask someone you trust to review the results. If they like it, you are on your way. Either find a publisher, or publish it yourself and offer it through Amazon.