Trying to display iMovie images on an Epson projector

Help-- I am trying to project an iMovie 10.0.5 project from my iMac (late 2013 version)

to an Epson projector EX7220

I used a mini display port to vga to connect to the projector and connected

BUT, the projector will only "see" and project my basic desktop - ity does not display iMovie.

Do I need to change a setting on my computer System Preferences ?

so the projector can "see" my IMovie?

Thanks,

Cynthia