Decals let you place an image onto the object surface like a sticker. Simply drag an image onto the shape, then select “Place as decal” in the pop up menu. You will get something like this:
Use the gizmo of two circles to move the decal around the shape, rotate and scale it. For more settings open the node properties panel for the selected decal node:
Here you can control decal parameters:
Use these options to fine-tune decals that you configured using decal gizmo.