If you and wife have been together 25 years, since high school, are you her only romantic/sexual partner, and vice versa? I can see why you are both curious about what is out there.
This is a board for polyamory, not for just open, sexual relationships. So part of getting ready is understanding how each of you will feel when the other has sex with others, and also, potentially, falls in love, or at least becomes infatuated with another, or more than one other.
Do you have kids? Do you have plenty of free time and money to date? Have you decided where the sex will happen? At your house or somewhere else? Are you prepared to date lots of duds before you find a keeper? Are you prepared to struggle with jealousy and envy, fear of loss, FOMO, etc.,etc.?
Have you or she done any reading of books about polyamory or ENM? Read any websites, listened to any podcasts?
Are you aware that women, even poly women, are wary of dating a married man?
Just fantasizing about opening up is one thing. Actually having the resources and skills to do it is something else entirely.
I'd start by reading some books (or listening to them): Opening Up, Polysecure, Sex at Dawn, Non-Violent Communication, are a few good ones.