This is a great question. Barnabas is found in several places in the New Testament. In fact, his name is found 28 times in the New Testament. And 26 of these times is found in the book of Acts.
In the book of Acts, he is one of the people who sold some property and laid it at the apostle's feet to help those in need. It is no wonder that his name means "son of encouragement."
Also he plays a pivotal role as he welcomes Paul after this conversion. The other Christians were afraid of Paul, because in his former life. According to the book of Acts, Paul persecuted the church. For example, he was present at the stoning of Stephen. Barnabas was able to see beyond this and he poured out love and accepted Paul.
He plays another important role in that he accompanied Paul in some of his missionary journeys. So, he was a early evangelist of the church.