“…That which we have seen and heard we declare to you, that you also may have fellowship with us; and truly our fellowship is with the Father and with His Son Jesus Christ.” I John 1:3
The apostle John makes it clear that his purpose for writing this epistle is so his readers “may have fellowship with” the apostles (“us”) and with God “the Father and with His Son Jesus Christ” (1:3). He is not writing to non-Christians to tell them how to get saved. He is writing to Christians to tell them how they can have fellowship or closeness with Christ.
So instead of saying that a Christian must “walk in the light” (1:7), “confess” his sin (1:9), “keep His commandments” (2:3), “love one another” (2:10, 3:14; 4:7, 21), “practice righteousness” (3:7, 9), and avoid “idolatry” (5:21) to get to heaven or know he is going to heaven, John is saying he must do these things to have fellowship (closeness) with Christ.
For example, one way for Christians to know that they have come to know Christ more intimately is by keeping His commandments (2:3). But even if you are not obeying the Lord you can still know you have eternal life because the only condition for eternal life is believing in Christ (John 3:15-16, 36; 6:40, 47; 11:25-26; 20:31; et. al). However, you will not have assurance that you are growing closer to Christ if you are living in disobedience to His Word.