Paul and Barnabas, arrived at the town of Antioch in the center of what is now Turkey. There they were invited to speak in the synagogue. Speaking for both, Paul said that he and Barnabas were witnesses to Jesus, who returned to life after three days in the tomb.
More pointedly, he said that he and Barnabas had come to give the good news. (Our word Gospel is old English for Good News.)
There were two parts to the good news Paul and Barnabas had come to reveal. The first part of it was that Jesus had overcome death. The second part of the good news is that Jesus will pull us through death to life beyond. We just need to get strong holds on him.
We use the word Gospel to describe the long accounts of Matthew, Mark, Luke and John. We use the word Gospel to describe songs with an inspirational twang to them. Really, though, Paul rightly restricted the word to the good news that Jesus can bring us through death to a happier life beyond this life.
There is no other way there. As Jesus said in the Gospel, “No one comes to the Father except through me.”