1 john 1:2 (For the life was manifested, and we have seen it, and bear witness, and shew unto you that eternal life, which was with the Father, and was manifested unto us;)
3 That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ.
Here we see John doing what he most wants to do and that is to get people see who Christ really was. That through the crucifixion we gain salvation by putting our faith and trust in Jesus and gain eternal life in Heaven. He lets us know that Jesus was with God in the beginning and God sent Him to be our Savior. John wanted people to listen to him so they could come to know the fellowship we can have together as believers in Christ. Having fellowship with other believers helps you to get closer to God and Jesus and helps your relationship with the Father and the Son grow.