How to deal with buttons with Physic2D and Imgaes(PNG)?

I want to know how to create button with my Images(PNG). I'm not gonna use the GUIButton because of creating the default button image.

I copied the images in my Unity Project and changed to sprite(2D and UI). Then, create the sprites simply by dragging. I also added the script which includes 'onTouchDown() and onMouseDown'. However, it didn't work so I tired again with layermask but it didn't work as well with no error code. Maybe the physic2D is the reason.

How can i make button with simple image. Could you guys help me to do so> Please let me know does anyone have idea. Thank you.