Christians really hold an incredible privilege in this world: We represent Christ to the world, serving as His holy ambassadors!
Paul is quite clear that his gospel message is all about Jesus Christ. Christ came precisely for this purpose - to remake the world in newness, reconciling it to God. Christ is the means and method for this reconciliation, and we are the messengers. The role for the Church is not to do what only Christ can do (i.e. reconcile the world to God); rather, our job is to spread that message, serving as Christ's ambassadors, to those who have yet to hear and respond to His amazing work.
And this is our message: "We entreat you on behalf of Christ: be reconciled to God!" As you read these words, you are in a position to either 1) respond affirmatively and be reconciled to God, or 2) join the team of the Church and do what you can to get that message out! Become an ambassador of Christ!