Hi, your friendly mod here. Since you said you wanted to learn (as well as hopefully find a MM couple to date), I moved this to the section where we can share information and support. I don't believe we have a ton of bisexual MM couples coming here looking for a woman to share, since this isn't dating site, per se. But good luck with that! Maybe your inbox is blowing up!
Doing polyamory usually isn't just a matter of finding an already-established couple and starting to date both of them. You would be what is called a unicorn, a single female who wants to date both members of a couple. Usually she is looking to date a MF couple. In your case you imagine you'd find a MM couple, and you are attracted equally to both of them, and they are both equally attracted to you. Once the first couple dates have gone by, you'll start to see if you're compatible with either or both of them, and they'll see if they, individually, are also feeling the same for you.
The problem is, usually it doesn't work out to be that balanced. Almost always, one dyad (you, and one of the guys, in this case) would click, whereas you may not like the other guy as much, or he might not be that into you.
That's the first problem most people looking for triads run into.
What is much much more common and successful is a MFM V, where you are romantically/sexually involved with 2 guys, but they are not involved with each other. In this case, you'd start to date one guy, as an individual. Then another guy would come along that you're also interested in dating. Now, eventually maybe you'll have these guys meet each other, say, you all have coffee together. They may like each other. They may not. If they get along, you could have "kitchen table polyamory," where you 3 can all hang out and have dinner, do an activity. But you don't all have sex together.
If they do get along well, maybe somewhere down the road you'd want to try threeway sex. If the guys are bi, maybe they'd start to be attracted to each other (as well as to you). Then you'd have a triad. But it's more likely to remain a V.