Eh, this isn't a big install, although if you're a bigger guy/girl laying down and installing it is kinda a PITA. The instructions from Cusco are pretty straight forward. Here's some pics that may help you proceed.

 Only 2 tools needed.

Allen wrench

7mm wrench



What you get in the box



First clean your gas pedal with a metal cleaner or hell, windex would probably work good.  This is to have a nice clean surface to adhere the foam pad onto the pedal.  



Peel the backing of the pad and place on the pedal.  



Now take the screws and nuts and place them in the appropriate holes on the pedal itself.  Tighten them just enough to give you room to slide the pedal on.  



Now the annoying part.  You'll have to crawl underneath the tight confines of your FR-S/BRZ and slide the Cusco Pedal on to your gas pedal.  Once you have it lined up properly and ensure that the mounts are properly touching the back of your pedal. Use the 7mm wrench to hold the nuts down as you tighten them with your allen wrench.  This is the most difficult part mainly because it's the most uncomfortable.  

Once you're done, make sure it's tight, and try out how much easier it is to heel-toe!



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