I have been fantasizing about women a lot lately and my husband thinks we should try to find a third. I've done 'some' things with women but not fully been with. I'm nervous about the idea but also really want to give it a go...
If you and your husband both want to try this, it sounds like something worth trying out together! Remember that a "third" would not be a sex toy for you two to use to figure stuff out and have new experiences together - she is a person with needs and feelings as well. Not many bi/pan/lesbian women wake up thinking "boy, I'd sure love to be a compliant, useful sex being to help a woman and her husband do what they want together!" But a lot of people are interested in a sexy experience with some hot, fun, responsible, attentive, giving people.
Consider starting out with fantasies - watch MFF porn together or read erotica and talk about it. Write or talk out sexy fantasies about a threesome. Use that as a springboard to talk about what you really want (a one-night threesome? a frequent sexual partner? a dating relationship?) and how you want it (how involved will your husband be - watching? participating? hearing about it afterwards? what is negotiable on this?) so you have a clearer idea.
Then check out the resources here - really, thoughtfully, read and discuss them. Get your business on lock, then be respectful, responsible, and patient. And best of luck!