All members of the Church accept part of the charge to take the gospel of Jesus Christ to the world. Full-time missionaries teach those who are not yet members of the Church. Members of the Church are to find those the Lord has prepared for the missionaries to teach.
And the promise of great joy for the faithful missionary is also ours as faithful members who give our hearts to missionary work:
“And now, if your joy will be great with one soul that you have brought unto me into the kingdom of my Father, how great will be your joy if you should bring many souls unto me!
“Behold, you have my gospel before you, and my rock, and my salvation” (D&C 18:16–17).
There are many ways you can help find people for the missionaries to teach.
Pray to be guided by the Holy Ghost.
Be a witness at all times in what you say and do that Jesus is the Christ and that God answers prayers.
I testify that the Holy Ghost will direct you to those who seek truth as you pray and work for that guidance. And I know from experience that your joy will be lasting with those who choose to take the gospel into their hearts.