** The steps in this article only apply to SharePoint Communication Sites! **
The Hero Webpart in SharePoint Online Communication Sites is great - it gives you a nice way to present regularly used links to your end users - see below:
But wait .... ! There's a problem - see the big swathes of white space on either side of the Hero Webpart? How do we get rid of those? It's not immediately obvious!
As with most of these kinds of things, it's pretty simple - you just gotta know where to look.
So Edit your page, and add a new Section by clicking the + icon at the top left; make sure you select the Full-width section as shown in the screenshot below. If you don't see the Full-width section option, you're not using a Communication Site!
Now, drag your Hero into the new Full Width section, Republish your page and - voilà! - your Hero is now Full Width! Easy!