There is a "referral" link in your account that you can give someone. When they register, the "Referrer" field should be automatically populated with your username. If not, they can add it manually. You will get 5% of what they make. It doesn't reduce their amount since it comes from Rumble.
I'm not sure if it's 5% of what the creators bring in, or 5% of the total revenue (Rumble's share + creator's share). But either way, it doesn't cost the creator anything. It comes from Rumble's share.
Maybe Mario would be kind enough to clarify what it is 5% of.