Boyfriend and I think we want a threesome...help!

Jacquie • "Tragedy is a Comedy Misunderstood" Actor and Screenwriter in Grand Rapids Michigan
Hey guys! 
So I've been having some interest in experimenting with a threesome. My boyfriend is down but a little hesitant. I am too, new things are scary! Plus we both see sex as a pretty emotional thing at its roots. We are both interested in pursuing this as a fun and new possibility though!
Has anyone on here ever had a threesome? How did you find the right girl (aka a "Unicorn" so I'm told) and what boundaries did you set? Basically how do you recommend a first timer go about this process? 🙈 
Thank you!!❤️