For most LibGuides, side navigation is encouraged as it makes it easier for users to navigate the guide.
Selecting the Layout for a new Guide
To create a new LibGuide with side navigation, select the System Default - Side Nav Layout from the template options on the screen where you create and name your new guide:

Changing the Layout of an Existing Guide
To change the navigation in an existing guide to side navigation, open the guide you wish to change (and make sure you're logged in). Go to the top right corner of the screen and click on the Guide Layout icon (it looks like a small rectangular picture) and select Guide Navigation Layout from the available options.

This will open a pop-up window where you can change your template from tabbed layout to the side navigation layout:

Important Note: Changing navigation styles will automatically re-order the boxes on your guide, but not necessarily in the way you would choose. When you change your navigation to or from Side Nav, you will want to re-order the boxes on your guide so that they are in an order that makes sense.