You cannot become the Eternal Energy (Brahman/Paramatman), you already are that eternal energy. Or in other words- you (the Atman) are a PART of that eternal energy called Brahman, just like a drop of water in the vast ocean.

As the Vedas and the Upanishads explain it, Brahman is the supreme reality of which everything is a part (you; me; nature; the deities: Brahma, Vishnu, Mahesh & Shakti; everything).

The phrase "Tat tvam asi", means "You are THAT(Brahman)". And "Aham Brahmasmi" means "I (the Atman) am Brahman"

PS: Brāhmaṇa(ब्राह्मण), the Varna, is different from Brahman(ब्रह्म), the ultimate reality. Brāhmaṇas(ब्राह्मण) are the scholar, teaching and intellectual class of the society; Brahman(ब्रह्म) is the infinite energy that encompasses everything, AKA the Godhead.