What are the Question Tags?
When you look at the "Ask a question" page you used to ask a Question you will see that there is a Tags section near the bottom of that page. If you start typing something like "harlo" (without quotes) in the text field a list of potential 'tags' will be displayed for you to select from.
but don't understand which bit to copy
The example contained within the recipies page is written using Twee Notation, which is described within the cookbook's Common Terms section.
The Using the Twine Cookbook section explains how to download and import the recipe's Live Example into your Twine 2.x application so that you can view the different parts that make up the solution.
For that specific recipe the contents of the TWEE Notation example would be broken down as follows:
1. The CSS contents of the UserStylesheet passage wout be placed within your project's Story Stylesheet area.
2. The TwineScript contents of the Start passage is just setting up some test data, if you wanted to use it then you would place it within the main passage of your project.
3. The TwineScript contents of the Sidebar passage is what will automatically be displayed within the 'side-bar' area, simply add a footer tagged special passage to your project and copy this passage's contents into it. You can name this new passage whatever you like, but the solution named it Sidebar so it's purpose was clear.
It is the (append: ?SideBar) macro call and the built-in ?SideBar named hook that is responsible for updating the contents of the 'side-bar'