If you have found out that your partner was unfaithful and you want to make it work prepare for a long hard road out of hell. There is going to be a lot of trust lost that will have to be gained back. Both partners are going to have to swallow their pride. You may even have to admit how something you did played a role in their infidelity and this is not something a lot of people want to do. If you want to save your relationship however, it may be necessary. It is very emotionally damaging to find out someone has been unfaithful so take your time when deciding that you want to take them back.
When the affair is brought to light your partner needs to reassure you that they will never talk to that person again. They will never see them, talk to them, and they will do their best to put them out of their mind. You are going to have to overcome your resentment to the person if you want to make it work. It is going to haunt you for years, and that is something you should just go ahead and get used to. If you make the decision to stay in the relationship you are saying that you are putting your resentment aside and you have to keep that promise.
You will have to accept that things are not going to be the same after the trust is broken. You will have to rebuild your relationship for years before it will get back to the way it was before. If you are willing to accept this and know that you are going to have to work hard every day to get the relationship back to where it was. As long as you are both committed then you can recover from an affair.