Threesome advice?

I've seen many woman on here post about threesomes and their experiences. I'm looking for some advice. Me and my boyfriend have decided to go forward and try and have a threesome. He has given me the task to find a girl (we similar taste in woman) I'm bisexual by the way. Lol. I know we're gunna need rules and boundaries but idk where to start and need a little help on where to get started I guess. Lol. Any advice is welcomed, if you and your partner have had a threesome/s I would love to hear about your experience good and bad and how it affected your relationship. Thank you. 💕