Step1: draw a rectangle on the canvas using the rectangle tool. 

Step2: select the transparency icon to the right of the canvas, click on the gradient tab. 

apply the following settings. Change the angle to -90 degrees. Change the middle square to light gray and the too outside squares to medium gray by double clicking and selecting the color.  

Step3: Create a grain texture by selecting Effect > Texture>Grain. 

Step4: Adjust settings to the following Intensity: 7, Contrast:1, Grain Type: Horizontal   

Click Ok.