It's very simple:
-God's role in evolution ends with humanity becomes spiritually-inclined.
-God begins his relationship with humanity. Adam and Eve (or "Adam and Eve") are (represent) the first man and woman (humans) that have a relationship with God
-They are tempted to not follow God's rules by a snake (their own cunning) and they break God's rule due to a conscious decision. This means that Adam and Eve (humanity) no longer have a pure, perfect relationship with God. Their disobediance breaks their souls, as they are now no longer able to follow His rules and will without help.
-God sees [and knew beforehand] that Adam and Eve (humanity) break His rules, but fairly tries them. He then must help them and their descendents (all the rest of humanity; here the literal Adam and Eve/non-literal Adam and Eve merge) do what is truly right. He tries at first to give them a strict law to follow (Torah) but this doesn't work, despite prophets, sybil, and various other sages.
-Eventually, God the Son incarnates as Jesus of Nazareth, our Savior, to redeem us in Him. Jesus, being 100% God and 100% Human yet having one cooperative will without any one side dominating the other or being submissive or subtracting of itself to/for the other, makes the perfect sacrifice as He is God whose bridged humanity with Him. He lived a mortal life, being tempted constantly but never giving in. Upon the cross, He died for all our sins, so that in Him, we too can be saved.
-Upon baptism, we confess that He is Lord and we are therefore joined in Him in both death and in life. Baptism begins the regeneration of our broken souls; slowly "repairing" them. This "repair" is completed upon the Judgment; those who accept God's Grace and are therefore found to be righteous have their souls fully restored because with Him, they too were raised out of death into new life.