Complex sentence: He meditated on Krishna who appeared to him in a vision in the form of Shrinathji and disclosed the'Brahma Sambandha' (Sanskrit for- "Relation with Brahman, the supreme Godhead"), a mantra of self dedication or consecration of self to Krishna.
Split into simpler sentences: He meditated on Krishna who appeared to him in a vision in the form of Shrinathji. He is said to have heard the'BrahmaSambandha' mantra, a mantra of self dedication or consecration of self to Krishna.