Krishna delivers the method. That supreme being — within whom all creatures reside, and who pervades this entire universe — can be reached only through ananya bhakti: single-pointed, undivided devotion.
"Ananya" means having no other support. A small child holds on to the mother's hand and walks. The child does not need any other support — the mother is enough. Ananya bhakti is exactly like that: God alone is the refuge, the anchor, the destination.
And what kind of being is this supreme Purusha? All creatures exist within Him, and He fills everything that exists. The ocean holds all the waves, and all the waves are made of ocean. God contains all of creation, and creation is saturated with God.