Cubase LE is included with the Scarlett Studio Bundle and requires installation and activation from the Steinberg website. The guides below explain how to install, register and activate Cubase LE.
If your bundle came with Cubase LE 6 (on a physical CD) see this guide:
Cubase LE 6 Startup Guide PDF
If you have any problems with this having worked through the relevant guide, contact Focusrite support here.