In a perfect world, people wouldn't need gods. But perfect worlds can't exist and sooner or later someone, in trouble, desperate, will pray to the heavens. This is what happens in the beginning of Black & White.
Your new tribe bow before you in awe, and from this moment your prayer power starts to grow. As you carry out godly acts, the belief in you rises and more and more people are convinced that worshipping you in the way forward. But you can be good or evil. You may choose to rule the world as you wish.
As you grow in power, you acquire a Creature, a wondrous being capable of doing anything you can do. Capable of learning and being trained and capable of making his own decisions. The people of Eden, whether they believe in you or not, can't failed to be impressed by this beast, and more are swayed to your cause through their admiration of the Creature and the god that owns him.