How can we know how to do what's right? Many people believe they have a conscience or some type of internal guidance system. We do, in fact, have a divine influence within all of us, helping us discern right from wrong. It's called the Spirit (or light) of Christ:
"For behold, the Spirit of Christ is given to every man, that he may know good from evil; wherefore, I show unto you the way to judge; for every thing which inviteth to do good, and to persuade to believe in Christ, is sent forth by the power and gift of Christ; wherefore ye may know with a perfect knowledge it is of God" (Moroni 7:16).
For more, I encourage you to watch this video on light, in general, and the light of Christ, in particular. I'm confident you'll really enjoy it.