"Be not wise in your own eyes; fear the Lord, and turn away from evil.
It will be healing to your flesh and refreshment to your bones.
Honor the Lord with your substance and with the first fruits of all your produce" (Proverb 3:7-9 RSV).
What is the tree of life and where can it be found?
I can't relate your question to the passage you cited. I don't see the tree of life mentioned. The tree of life first appears at Genesis 3:22, when Adam and Eve are expelled from the Garden. The Lord is worried that they might eat of the tree of life "and live forever." I understand this to mean that if they eat of the tree of life at too early a stage of the spiritual journey on which they have been sent, they would 'live forever' in a state of limited understanding, at best. It is to prevent that the tree is guarded by cherubim with flaming swords. The tree is not mentioned again until the very final chapter of the Bible's final book, the Revelation to John. Here, at 22:2, the tree of life is in the center of the City of God that is now expressing as a result of the discoveries and choices we have made along the way. Now it is unguarded, and its fruit is freely available. Now we have completely remembered the Truth of our spiritual identity, and we can safely claim our immortality.
As for the passage from Proverbs, it is an expression of what is, really, the entire theme of the Bible: Put God First! When we make that our highest priority, then everything else falls into place and our experience is 'healing' and 'refreshing.'