First steps in a trio

Good people! It's been a long time since I've had an account but only as an observer, I didn't use it much until recently when I started to get excited with all the material. Let me tell you that I'm 26 years old and have been in a relationship for almost 6 years (my partner is one year younger) and we've been living together for about 2 years approximately. Sex has always been good, never had any problems with it, it intensified when we moved in together, normal stuff. But one day we were talking and the topic of threesomes came up (something we'd never talked about before). I don't know if she slipped or prepared it but my partner told me that her work friends talked about it and they started asking who would have a threesome with, then I asked my partner what she said and the answer was: obviously with a woman! And there I stopped, (obviously the fantasy of having two women) and we started talking more deeply about the topic, started fantasizing about her friends, sex became very hot and better every time. We came to the conclusion that both wanted to have a threesome, obviously I wanted her to bring her friend (always in a crazy fantasy, don't know what her friend wants) but she insisted it had to be a stranger, so here's why I'm posting, since there are many experienced people on Pornga about this topic, I'm looking for advice on how to take this fantasy forward, where is the correct place to find a third person, if these things happen miraculously or any advice you can offer will help, or if there's a woman willing to participate she'll be welcome, hope not to have bored you and that you can give me a hand, I'll upload some photos of us soon.