Step one:
The first thing that you need to know is that you don't need to immediately consider divorce as the only alternative. What you are going to need to do is to decide if you want to stay with that person and work on forgiving them or if you want to leave. But if you do decide to stay then you need to make a personal commitment that you are willing to try to forgive them.

Step two:
The next thing that you need to do is to confront your spouse and tell them that you know that they have been unfaithful and let them know how this makes you feel. When confronting your spouse you are going to want to make sure that you can do it in private so that nobody overhears and that you won't be interrupted. But in this conversation you are going to need to find out if the affair is over and whether your spouse wants to fix the relationship.

Step three:
The next thing that you are going to need to do if both of you want to fix the relationship is to seek counseling. The good thing about counseling is that you can do it together or you can attend by yourself if your spouse is unwilling to go and it is still beneficial.

Step three:
Most likely counseling is not going to be enough so you are going to want to do plenty of research on the subject which will mean you need to read books on the subject. The more knowledge you have on how to move forward, the more likely you'll be able to achieve it.

Step four:
You are also going to need to get some kind of support from your family members or close friends. But you are going to want to be sure that you trust the person you are getting support from because not everybody thinks you should forgive an unfaithful spouse. You are going to want support from people who are not going to judge you or your spouse for your actions.

Step five:
Something else that you are going to want to do is to write down your feelings in a journal or share them with your spouse. Most likely you are going to feel an assortment of emotions that are going to range and sometimes writing them down will give you a better grip on your feelings and will allow you to handle what is coming a lot easier. Not to mention it can help you to let go of any negative feelings that you might still have.

Step six:
You are also going to need to realize that many marriages survive a spouse being unfaithful and those marriages go on to continue in a healthy relationship. So as long as you are both working towards repairing the relationship then the chances are high that you will succeed.

Step seven:
Understand the stages of grieving over your spouse being unfaithful will be almost identical to the stages of grief you would experience if your spouse died. Some things that you might go through are denial, anger, bargaining, depression and acceptance, and what you need to realize is that all of these feelings are a part of your forgiveness process. If you are able to understand these steps, you are more likely to get through them.