Featured assets are the assets (image or video) showcased at the top of the Home Page.
To replace the featured asset ensure that the ‘Is Featured?‘ checkbox is ticked within Asset Details.
To see a list of all assets that have been flagged as ‘featured‘, go to Admin->Content->Manage featured assets.
You will need to untick the checkbox for any existing featured assets to remove them. If you leave them ticked, the featured asset will change to the next in the list each time you load the homepage.