Welderguy;
If I offer you a new truck, for free, as a free gift, all you have to do is believe that it is a free gift and come get it.
Acts 2:
37 When the people heard this, they were cut to the heart and said to Peter and the other apostles, “Brothers, what shall we do?”
38 Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit. 39 The promise is for you and your children and for all who are far off—for all whom the Lord our God will call.”
If you don't believe what I have told you, then you will not come, the only way to believe is to believe me. The Holy Spirit convinced many that day and they were baptized for the remission of their sins.
Salvation belongs to the Lord, who does he call? He calls everyone. (2 Peter 3:9)
But we have to respond. No where in Scripture are we called to believe and then do nothing.
And to your opening, yes salvation is available to everyone, "You, your children, and all who are far off". We were dead in our trespasses, but he "quickened" us, he made us alive just as the Holy Spirit made those on Pentecost "Alive". Once quickened you have some choices, (1) say "no thank you" and go back to sleep, (2) say "thank you but i am not going to do anything so you bring it to me, (3) say thank you "what shall I DO".
You're missing the kingdom in all of this. Remember the kingdom parable of the sower. ...."some fell by the wayside....some among thorns...some on the stony ground....and some fell on good ground"?
These men in Acts 2 are displaying this very parable. Do you see that?
It's not even about their eternal salvation here. I know this because Jesus, while on the cross, cried out "Father, forgive them, for they know not what they do". He was dying for these exact same people. They were forgiven and redeemed forever.
On Pentecost, some had been regenerated, thus they had "good ground" for the words of the kingdom (seeds)
Others did not have good ground, for whatever reason.
Do you see why I keep saying most of the New Testament is speaking of the kingdom here and now? Most people think it's speaking of obtaining eternal life. That part is finished. Jesus said so.