16 For I am not ashamed of the gospel, because it is the power of God that brings salvation to everyone who believes: first to the Jew, then to the Gentile. - Romans 1:16
The servant of God Paul speaks some very powerful words that he is not ashamed of the gospel because it is the power of God to bring salvation to everyone who believes. The key here is that the gospel is the power of God. The dictionary defines the gospel as "the teaching or revelation of Christ".
Paul knew this first hand because Christ revealed Himself to him personally and from then on, he received salvation because he believed. Paul's journey to salvation was not the smoothest. He encountered Jesus Christ and his life was changed. Paul explains in Acts 26:16 that as he was on the ground after being blinded by a bright light, he heard the Lord tell him that He had appointed him as a servant and as a witness of what he had seen and will see of Christ. This is a clear example of the power of God to bring salvation to those who believe.
The key is to believe. Without believing, we cannot experience the salvation of God. We need to believe that the gospel is powerful and after we have believed, we should no longer be ashamed of the gospel. We should proclaim it to all nations without shame or fear. Paul went on to proclaim the word of God without fear and became one of the greatest apostles that ever lived.
God can also use each one of us in the same way as Paul if only we believe and are not ashamed of the gospel!