John 10 describes Jesus as the Good Shepherd and Christians as the flock of God. It repeatedly describes the relationship between the Shepherd and the sheep in these ways:
Jesus knows His sheep (10:3, 14, 27)
Jesus caringly leads the sheep (10:4, 11, 15, 28)
The sheep know the voice of Jesus and follow Him (10:3, 4, 14, 16, 27)
This is instructive to churches because sheep are gathered into local flocks in the local church, and in that local flock they follow their Shepherd. When we see how this passage describes the sheep, we can understand what the church should do in order to help the sheep grow and increase.
The sheep follow the voice of Jesus and are gathered to the voice of Jesus. So if the church is the place where the sheep of God gather locally (the very word church means gathering in Greek), then the church must proclaim the word of God if it expects the sheep of God to gather and grow. It must proclaim the word of God rightly, according to how Jesus taught us about the Bible in Luke 24 - that all of it points to Him. And as the church proclaims the word of God, both corporately during gathered services and indivually throughout the week, the sheep of God will hear the word of God and be drawn to follow God in the abundant life that He came to give (John 10:10). That is how John 10 talks about church growth - it says that the flock of God will grow (sheep will experience abundant life and other sheep will be brought in) as they hear the word of God. This means that the word of God must be central to our mission and method of church health and growth.
If we fail to rightly proclaim the word of God, then it will actually be harmful to those who are gathered. This passage says that voices other than the voice of Jesus are actually strangers, robbers, and thieves, and they will lead to robbery, death, and destruction (John 10:10). So it is vitally important that we speak the word of God and center everything we do around the word of God, because that will be the difference between abundant life and death.
On a church level, this means that every gathering and every ministry must be primarily focused on proclaiming the word of God. This will look different in different contexts, but in all that we do we must not expect something else (whether that be certain aesthetics or types of programs) to be the reason that we grow. The word of God is what we need to experience growth.
On an individual level, this means that we must speak the word of God so that the people around us hear God's word and are drawn to Him. Luke 6:45 says that the mouth speaks out of the abundance of the heart, and so if we want the word of God to overflow out of us, then it must be embedded in our hearts. And when we have hidden God's word in our heart, then it will flow out of us. Talk about the sermon from Sunday, talk about what you've been reading in your personal Bible reading, talk about what the Bible has to say on that topic that your friend brings up. As we do this, people will hear the word of God and be drawn to the flock of God.
It is good news that God's plan of growth is through the word of God. It means that we always have what we need in order to grow personally. It means that we always have what we need to grow as a church, no matter what our other resources may or may not be. God plans for us to grow through His word, and that means abundant life for us and glory for God.