One way I think of it is vill means wants to. So, if you add ha it means wants to have.
Vill usually goes with verbs: Han vill äter myron (He wants to eat ants).
Vill ha usually goes with nouns: Han vill ha en ny klänning (He wants to have a new dress).
But in English, we usually just say "wants" instead of "wants to have". You need to mentally equate the "to have" part with the Swedish "ha" part.
Hope that makes sense! And please correct me if I'm wrong.