We're rolling this feature out to more channels. If your channel met all the requirements stated here: https://yt.be/help/tmhG , you'll be notified once the feature is available for you. If you're eligible for channel memberships, here's how to turn it on: https://yt.be/help/4enU
My Channel meets all the requirements but I am not eligible for it right now , please boost this process , or tell me someone who can forward my request , please and thank you