In this verse, Paul refers to his status as a prisoner - he wrote this epistle when he was incarcerated in Rome. A believer must hear the Word of God in order to perform any function in the Christian life, including worship and service to Christ. Worship is the ability to hear and think about God's Word while under the control of the Holy Spirit. God is a Spirit, and they that worship Him must worship Him in spirit and in truth. When you stop concentrating on the Word, you stop worshipping.
Worship demands concentration, learning, understanding.
Your ability to worship depends on what you understand about God, about Christ, and about the Holy Spirit. It depends on how well you understand God's plan for your life and how you are to function as a believer. Worship includes singing, giving, praising, teaching, and other activities. Worship can be accomplished privately, alone with onesself, or with a group of other Christians. God gave to Paul the knowledge of His grace so that Paul could communicate it to people.