Footer blocks are a way to promote additional content and are displayed in the Help Center footer. In the following screenshot, Want to build a help center like this one? is a footer block:

To create a footer block, head to Help Center Settings and select the Footer Blocks tile.

From this screen, you can change the order of the blocks or create a new one.

Click + New Footer Block to create a footer block.

Title: a title to introduce the block.
Description: a description to provide more context.
Call to action (optional): this will create a button and the label of the button will be the text you enter here.
Call to action destination: the URL where you want the button to lead .