The church's policy can be found on the church's beliefs page: What We Believe
"We Believe that God created man and woman as unique biological persons made to complete each other. God instituted monogamous marriage between male and female as the foundation of the family and the basic structure of human society. For this reason, we believe that marriage is exclusively the union of one genetic male and one genetic female, sanctioned by the church and recognized by the state as evidenced by a marriage ceremony."
Additional details on the church's non-affirming policies can be found in these sermons: