The marriage is the important thing. You must have a truly solid foundation to go for this lifestyle full time. Straighten out the marriage and explain things to him first. Then, when the marriage is back on solid footing, enjoy.
Both of you have to be on the same page. Bringing in an additional person or persons into your relationship will make things more complicated. If you have a strong relationship it can add to the joy and pleasure in your life. It can also destroy a relationship if you aren't working from a strong foundation.
Realistically neither of you have been dating for quite some time. Certain skills that are required to do so are rusty or absent. If you and your husband decide that you want an additional person or persons in your relationship I would recommend locating a swinger's club for a number of reasons. First of all there is no doubt why anyone is there. Nobody is likely to be concerned if you are dressed at your slutty best.Most likely any crude or abusive people have been weeded out. You are likely to meet someone who can point you in the direction of a good bull for your first encounter. If you want someone in you that is a lot larger than you are accustomed having a skilled fucker is important. Most clubs offer no pressure, if you become uncomfortable no is likely to force you into anything. Clubs fall into two categories on premise and off promise swinging. With an on premise club you can meet and engage in sex on site. Usually there is an orgy room (my favorite) and then more private areas for couple or smaller groups. One advantage is that you have other people around you that add a sense of security. An off premise club you meet and go somewhere else. NEVER EVER bring a stranger into your home or go to a strangers home. Get a motel or motel room. Clubs are generally first name only, and don't be surprised if you see someone you know if you swing close to home