Threesome advice

So I've been single a little of a year now but had a FwB female. One day me her and one of her friends also female were drinking. Things happens and both of them gave me a bj. And that was as far as it went. But even after the three of us always hung out and the conversation of what happen would come up. I often would bring up having a threesome something I never experienced. They would say no. I since then moved but frequently think of what it would be like to have one. So how do I go about having one?