How does a person come to believe the gospel?
A person comes to believe the gospel by first realizing they are a sinner, condemned in Adam. Upon hearing the word of truth—the gospel that Christ died for our sins, was buried, and rose again—the Holy Spirit opens their understanding, enabling them to believe. The moment they believe, they are sealed with the Holy Spirit of promise.
Les explains the order: every child of God first comes from being a sinner, a son of Adam, condemned already. As soon as we realize we're a sinner, we hear the gospel, and the Holy Spirit opens our understanding so we believe it. The word of truth is the gospel of your salvation—Paul's gospel that Christ died for our sins, was buried, and rose again. The moment we believe, the Holy Spirit comes in and seals us as God's brand upon us, becoming the very power of God within us. Les also notes this places us under grace, not law; grace is never licensed, but we are led and guided by the dwelling Holy Spirit.