You can clarify that God is the one who has chosen them. Alternate translation: "a people whom God has chosen" (See: [[rc://en/ta/man/translate/figs-activepassive]])
Here "darkness" refers to their condition as sinful people who did not know God, and "light" refers to their condition as people who do know God and practice righteousness. Alternate translation: "from a life of sin and ignorance of God to a life of knowing and pleasing him" (See: [[rc://en/ta/man/translate/figs-metaphor]])