This gift can be used when we teach a class. It can be used by parents to teach their children. This gift also helps us instruct others so they can understand the gospel. This has been the gift of prophets and apostles who have been called as special witnesses of Jesus Christ. However, others are also given this gift.
Every person can have a testimony.
It usually comes through the whispering of the Holy Spirit but may come in a dream or vision. Elder Orson F. Whitney saw a vision of the Savior in Gethsemane. He saw the great suffering of the Savior, and it caused him to weep. Then the Savior took him into his arms and blessed him. By the power of the Holy Ghost we may know the truth of all things.