The whole of the NT explains how salvation is obtained

Scripture explains how man attains salvation, and it also
reconciles all of the supposed contradictions concerning salvation …

First, all humans are born with an inherited sin nature (a “fallen” nature), e.g. Jesus actually told His disciples that they were “evil”.
The normal human being is incapable of believing the gospel of
Jesus Christ because the Truth of it is hidden from him … man is:
spiritually blind and deaf, spiritually dead, a slave to sin, forced to
obey evil, a captive to the law of sin and death, unable to be saved
through good works, deceived and blinded by Satan, a captive of
Satan unto death.

The gospel of Jesus Christ is “foolishness” to all those perishing
(going to hell). They do not choose this, but are just incapable of
believing the foolish gospel.

God’s grace (unmerited favor) toward all of fallen humanity is 3-fold:
• that ANY human could ever be received into heaven by a Holy God
• that SOME humans are given the ability to believe the saving gospel
• that sincere repentance can usually result in the forgiveness of sins

God must give a seed of faith to man to enable him to believe the foolish gospel. This is not a one-time event, but the Greek tense indicates a continuing belief. That only some are chosen is consistent with God’s preference, for example: “I dwell in the high and holy place with him who has a contrite and humble spirit”.
A question:
How-when-why did certain people obtain this type of spirit?

(*A*)
Along with truly believing the saving Truth of the gospel with his heart,
man receives the Holy Spirit within, and is born-again with a new nature. After receiving this free gift (a revelation of the Truth), the believer will begin to be taught deeper spiritual Truths by the precious Holy Spirit who dwells within. Man is no longer a slave to sin; he no longer has to sin; he can choose not to sin. He can present himself as a slave of obedience unto righteousness for holiness, or he can choose to present himself as a slave of sin unto eternal death.

One critical spiritual Truth is that disobedience to God is actually proof
of unbelief. In the OT, the Israelites did not enter God’s rest because of
disobedience (unbelief). God left them scattered all over the desert floor; and this was a warning for everyone! Born-again believers have much less of an excuse for failure … see (*A*) above.
So, here Scripture gives another negative response to the question of whether or not easy-believism and easy-grace are enough for salvation.

The main reason for God giving man free will is to test his love,
faithfulness, obedience, etc. to God his Creator. Yes, Jesus became
the author of eternal salvation to all who obey Him … and this obedience does not refer to believing in Him and His gospel after having received the precious free gift of saving faith. No, Jesus said that if you love Him (for His sacrifice, etc.), you will obey Him. The practicing of righteousness is proof that one stands righteous before God.

After receiving the saving Truth, the believer can always make the
disastrous free-will choice of not continuing on with his faith.
Many Scripture passages warn that enduring in the faith until death is
absolutely necessary for salvation. You must not fall away from the faith when the terrible persecution of Christians comes upon you,
and you must not take the mark of the beast of the antichrist.

It’s all about unbelief … and the NT describes exactly what unbelief is.
An evil heart of unbelief is displayed by one who departs from the faith, and this is often connected to one having been hardened by the deceitfulness of sin.

After receiving the saving Truth, the believer can always make the
free-will choice to be disobedient and return to his/her old lifestyle of
habitual unrepentant sinning. Several lists of sins, which many people
(including believers) commit habitually, apply to absolutely everyone
with regard to being disqualified from entering the kingdom of God
(heaven), which is somewhat analogous to heaven itself.

If you wish to see Scriptures for any of the points above,
please just ask.