Problems with touch input.

I'm creating a mobile game, but I'm having problems with touch input. With the UI, I've created successfully the player controller. But I want that, when the player sees an interactive game object, he'll be able to touch it and then something will happen. There's another problem, when the player touches a game object, the touch must ignore the UI. I've tried several online tutorials, but I can't find my answer. Thanks.

PS: Sorry for the bad gramar, I'm from Brazil.