How do you make evening primrose oil from the fresh flowers?

Evening primrose oil isn't actually made from the flowers; it's made by extracting the oil from the seeds.

I suppose you could distill an essential oil from the flowers but that doesn't sound like what you're talking about.

I'm not sure there's any practical way to extract enough oil from evening primrose seeds to make it worth your time and I'm not even sure how you'd do it without jeopardizing the chemical integrity of the resulting product.