How to take cap off oil ? (ford transit)?

Sorry if this seems like a really dumb question. But im trying to top my van up with oil, and looking inside the bonnet, there's only 1 black cap with oil can logo on, But i cannot see a way to take it off? Unlike my car, it wont screw, and i dont want to pull anything in case i break it.

Maybe the oil goes in another place? Any help Greatly appreciated!!

(Ford Transit 1998)