Welcome to the Decals example level! This level demonstrates ways in which Decals can be utilized in your levels.
To create a Deferred Decal Actor, drag and drop them from the Modes panel.
This is only accessible from the Modes panel if you're in Placement mode.
You then only need to apply a Decal Material, which is really just a regular Material that has had its Material Domain property set to Deferred Decal in the Material's Details panel.