Do I need to use silicon?
Which way do the center funnel-like openings in the gaskets gaskets point?
Can I place the spacer directly on the existing closet flange?

Do I need to use silicon? No

Which way do the center funnel-like openings in the gaskets gaskets point? If you're asking what I think you're asking the answer is down.

Can I place the spacer directly on the existing closet flange? Yes
Good luck, Tom