Jesus has just finished a speech at the temple where He reveals the differences between Himself and His listeners. And then, in verse 31, Jesus begins to speak exclusively to those who have believed in Him. The "you" in this verse refers to the true disciples of Jesus. The only way to be set free is to believe in Jesus, and the only way to truly believe and thus "know the truth" is to follow His example, becoming His disciples.
The freedom Jesus offers is not freedom from physical, social, or political restraints. It is a spiritual freedom from the bondage of sin. As humans, we are all sinners. Our greatest need is to be freed from the condemnation of our Creator and the bondage of sin. Jesus had provided us the way to freedom when He died on the cross to pay for the full price of our sins. All we need to do is believe in Him. 
Jesus is the way, the truth, and the life (John 14:6). If you live the truth, you will know the truth, and the truth will set you free from slavery and sin. Trust in the Lord, and live free!

Dear Heavenly Father, help me to live in obedience to Your word and Your will as I seek to learn more about Your truth. I know I've sinned, Father, but You have never abandoned me. Thank You for setting me free from the bondage of sin and accepting me as Your child. Please help me to learn more about You every day so that I can become a better disciple of Yours. 
In Jesus's name I pray. Amen.