How do you place a smaller background over the previous background on a new state.

Hello, I'm new to unity, and I'm learning javascript. Im making a game where I want to design the "Option menu" on which I intend to make a "Gray blury effect" over my main menu background when I enter it. I also need for my sliders and buttons on that menu to appear over this blurry effect.

Any ideas?

Thanks in advance!