Is there any way to check how big a certain layer on a psd is? I have downloaded this flat style macbook pro psd http://dribbble.com/shots/868066-Fla...ok-Pro-freebie to use in my portfolio. But dont know the easiest way to fit my screen cap of the websites ive made into the screen in the picture... (hope someone understand what i mean).

Is there a trick or do i have to cut and paste until it fits perfectly?

(photoshop noob)

thanks beforehand.