Raspberry Pis in Makerboxes come preloaded with Raspian Operating System. You do not need to install an operating system

Quick Start Guide 
Raspberrypi.org: downloads, community, help, forums, more  
Code Academy: create a free account and start learning  
Code.org   
Learn Raspberry Pi with adafruit  
Make: YouTube Channel 
Program with Python - Introduction to Python Programming 
Program with Scratch  
Raspberry Pi Projects from Instructables 
Raspberry Pi projects from Make: Magazine