dadyad bhuñjita va svayam
tambulam ca nivedayet
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One should offer all the prasada to a Vaisnava or offer him some of the prasada and then take some oneself. After this, one should offer the Deity acamana and then betel nut and then again worship the Lord.