How do people who are dead in sin receive Christ's life-giving power?

People dead in trespasses and sins are where the whole human race is. They remain dead until Christ moves in with His life-giving power. That power is triggered by faith in the Gospel. So receiving Christ's life-giving power comes when a person exercises faith in the Gospel.

Les explains from 2 Corinthians 5:14 that the love of Christ constrains believers because Paul's doctrine says one died for all, so all were dead. Les points out that the whole human race is dead in trespasses and sins. They stay dead until Christ moves in with His life-giving power, and that power is triggered by faith in the Gospel. Paul is writing to Gentile Corinthians, emphasizing this as his doctrine.

2 Corinthians 5:14

For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead:

When does a dead person stop being spiritually dead?

A dead person stops being spiritually dead when Christ moves in with His life-giving power. That power is triggered by faith in the Gospel. Until that happens, the whole human race remains dead in trespasses and sins, as Paul's doctrine states: if one died for all, then we're all dead.