How to enter the spiritual world, and in what way?

The Kingdom of God is a reality.

The Lord says: My sovereign abode is a spiritual and absolute kingdom from which there is no return to this material world. Whoever attains supreme perfection, engaged in serving Me personally with devotion in this eternal abode, attains the highest perfection of human life and need never return to this world of suffering.

Truly, no one can enter the Kingdom of God unless they have attained the state of holiness.

This is why God says: Be holy as I am holy.

One attains the state of holiness by practicing austerity, that is, not having illicit sexual relations outside of marriage, not eating meat, fish, and eggs, not consuming drugs and stimulants such as alcohol, coffee, tea, cigarettes, and not gambling.

The state of perfect purity is achieved by renewing the bond of love that unites us to Krishna, by loving Him, obeying Him, doing His will, linking our desires and interests to His, surrendering ourselves to Him, and serving Him with love and devotion.

The Lord says to this effect: Only through devotional service, and thus alone, can one know Me as I am. And the being who, through such devotion, becomes fully aware of Me, can then enter My absolute kingdom.

Only by serving Me with undivided love and devotion can one know Me as I am and, likewise, truly see Me. Thus, and thus alone, can one penetrate the mystery of My Person.

Knowing Krishna, God, the Supreme Personality of Godhead, as He truly is, in His personal, primordial, original, infinite, and absolute form, allows one to simultaneously know the absolute truth. This is why Krishna, God, the Supreme Personality of Godhead, is also called the “Absolute Truth.”

Also, knowing Krishna as He truly, is allows one who has attained the state of sainthood, the devotee, to obtain knowledge of all things.

Similarly, by visiting the supreme planet of Lord Krishna, one can know all the other planetary systems that lie on the path to Vaikuntha, the spiritual world, where everything is full of knowledge, bliss, and eternity.

In truth, the supreme planet, Krishnaloka, the one where Krishna, God, the Supreme Personality of Godhead, permanently resides, is larger than all the spiritual planets combined, and all of them float in the spiritual sky below the planet of Godhead. The spiritual world is three times larger than the material cosmos.