You may wish to invite the person to read 1 Corinthians 10:14-22, and 11:17-34, where Christians eating the Lord’s Supper is talked about.
The Real Presence is indicated especially in 1 Corinthians 10:16, and 11:27-29:
16 The cup of blessing which we bless, is it not a participation (or communion) in the blood of Christ? The bread which we break, is it not a participation (or communion) in the body of Christ?
27 Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord. 28 Let a man examine himself, and so eat of the bread and drink of the cup. 29 For any one who eats and drinks without discerning the body eats and drinks judgment upon himself.