Question: How Can Krishna Come From Himself?
I know Krishna came from Himself but I don't understand how can that be.
Answer: He Must Because There's Nowhere Else to Come From.
Krishna must come from Himself because there's nowhere else to come from. Since Krishna is the origin of everything and since He is also included with everything He must therefore originate in Himself. Since He is the origin of all, there can be no other cause for His existence other than Himself. In other words, He is self-manifested. He exists merely by dint of His desire to exist with no other cause.
Since Krishna is the origin of everything, if it were not for Him there would be no existence at all. There would be simply void. There is no example of anything else which originates from itself that we can give you as an example to help you understand Krishna's ability to manifest Himself. The understanding of Krishna goes completely beyond any sort of mundane logic. His mysteries are revealed to the sincere disciples through the transparent via medium of the bona fide spiritual master to those devotees whose eyes are tinged with salve of love of Godhead.
This is described as follows in the Sri Brahma Samhita:
santaḥ sadaiva hṛdayeṣu vilokayanti
yaṁ śyāmasundaram acintya-guṇa-svarūpaṁ
govindam ādi-puruṣaṁ tam ahaṁ bhajāmi
"I worship Govinda, the primeval Lord, who is Śyāmasundara, Krịsḥṇa Himself, with inconceivable innumerable attributes, whom the pure devotees see in their heart of hearts with the eye of devotion tinged with the salve of love."
So if you want to understand Krishna, kindly chant His sweet holy names every day with love and devotion:
Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare
Hare Rama, Hare Rama, Rama Rama, Hare Hare
In this way, by chanting with love, you will someday personally meet Krishna and be able to directly see by your own bhakti empowered perception how Krishna is the origin of everything including Himself.