"If any of you lack wisdom, let him ask of God, that giveth to all men liberally, and upbraideth not; and it shall be given him." James 1:5
You can know for yourself that these things are true by asking Heavenly Father in prayer. He will answer you through the Holy Ghost. The Holy Ghost is also called the Spirit of God, and one of His roles is to witness, or testify, of the truth. The Holy Ghost reveals and confirms truth through feelings, thoughts, and impressions. The feelings that come from the Holy Ghost are powerful, but they are also usually gentle and quiet. As taught in the Bible, “The fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, meekness, [and] temperance” (Galatians 5:22–23). These feelings are a confirmation from the Holy Ghost that this message is true. You will then need to choose whether you will live in harmony with the teachings of Jesus Christ as restored through Joseph Smith.
"President Brigham Young declared: 'The Spirit of revelation must be in each and every individual, to know the plan of salvation and keep in the path that leads them to the presence of God.'
So vital is this framework that if one stays or strays outside it, he risks provinciality and misery. In fact, most human misery represents ignorance of or noncompliance with the plan. A cessation of such mortal suffering will not come without compliance to it. Hence, the Lord, who has freely shared this vital knowledge with us, has urged us to teach the fundamentals of this plan “freely.”
The plan always points the way, but does not always smooth the way, since individual development requires an 'opposition in all things.' (2 Ne. 2:11.)
The Lord will give us the needed intellectual and spiritual confirmation concerning His plan, but on His terms and in His own way.
'If any man will do his will, he shall know of the doctrine, whether it be of God, or whether I speak of myself.' (John 7:17.)
Truly, of all the errors mortals could make, God’s plan of salvation is the wrong thing to be wrong about!
No error could be more enormous or more everlasting in its consequences!"
