Villagers spawn naturally in the game world in seeded villages. If you have built your own village in a location that was not a naturally generated village, villagers won't spawn by themselves. However, there are other ways you can populate your village with villagers. This is what you can do to get villagers to come to your village.
Use A Villager Egg
This option is limited to either creative mode or using cheats. If you obtain a villager egg, you can use it to immediately spawn a villager in any location you like. This means you can use it to populate the village with as many villagers as you like.
Transfer Them From Another Village
If you can locate a village somewhere else on the map, it is possible to transport the villagers from that village to your own custom built one. There are various ways in which you can do this depending on the distance. You could build a wall and try and lure them to come to your village if it isn't too far. The fastest, but slightly expensive solution is to use minecarts.
This tutorial will show you how to put a villager into a minecart so you can transport them to your own custom village anywhere on the map. This is probably the best way to get villagers to come to a village.