Hans' hack is remarkably easy to implement into your blog, since he has provided the code ready for you to copy and paste into the relevant sections.
In order to use the Table of Contents widget, you will need to alter your template slightly so you can add a page element to the top of your blog posts. This is so the table of contents can expand into this area, leaving your posts in place beneath.
After this, it's a simple case of copying and pasting code into HTML page elements in this new section, and also in a sidebar widget.Use this link to read Hans' post featuring the code and implementation of this great Blogger hack.
This widget can also be customised using CSS to alter the styling, which you would insert between the <b:skin> and </b:skin> tags near the top of your blog template (I will be doing this to my own CSS section shortly!).
This hack really is a great way to organise your blog posts in order to make it easier for readers to find posts they are interested in.