How to do it...

1. Visit Structure and click on Menus.
2. Click on Add menu.
3. Provide the title Sidebar and optional summary and then click on Save.
4. Once the menu is saved, click on the Add link button.
5. Enter a link title and then type the title for a piece of content. The form will provide autocomplete suggestions for linkable content:

1. Click on Save to save the menu link.
2. With the menu link saved, go to Structure, and then Block layout.

1. Click on Place block next to Sidebar first. In the modal, search for the Sidebar menu and click on Place block:

1. In the following form, click on Save block.
2. View your Drupal site by clicking on Home in the administration menu, and you will see the following menu: