Adding Light Leak Stock Footage Overlays

So, I'm pretty new to HitFilm, and I got a copy of Hitfilm Standard along with my purchase of Sony Vegas Movie Studio 11 a while back. Being rather clueless as to how to use HitFilm, I'm wondering if I can add light leak stock footage (found here) overlays to a video, since I'd need Vegas Pro to do it in Vegas.

I think I've got a very basic feel to HitFilm - I can create a new project, import clips, cut and rearrange, and make a new composite shot... But that's about it. I don't know how to operate composite shots.

If someone could walk me through (if it's possible), that'd be great. Thanks.