What does it actually mean to be risen with Christ?
To be risen with Christ means that when Christ died, the believer died; when He was buried, the believer was buried, in the mind of God. Just as He did not stay in the tomb, the believer is resurrected out and given new life, eternal life, to live forever in His presence.
Les explains from Verse 1 that being risen with Christ rests on what was taught back in chapter 6: when Christ died, I died and you died; when He was buried, we were buried, in the mind of God. Since we did not stay in the tomb any more than He did, we were resurrected out and given new life. Les connects this to chapter 8, where the word life means eternal life—living forever in His presence. He contrasts that with even a 90-year lifetime and says the book was left to prepare us for the eternity that is coming; materialism can keep young people in the dark, but that does not mean life cannot be enjoyed.