Female with a MFF fantasy

I’ve only been with men but have always fantasized of being intimate with a woman. (I can’t be the only female who wants to worship another woman’s tits or have have each others tongues in/on/around each other!) But I also have an extreme fantasy of a MFF threesome. Especially where her and I start and he watches and masturbates to us. How do I find a couple who is looking for that? Just the websites and apps that are out there? Any recommendations from couples or females who have had success finding this?