Chapter 1 - First Beeps
Installing SuperCollider
Download SuperCollider for your platform and install it.
(There is a great set of introductory examples on that page to play as well.)
On starting SuperCollider you will see three panels opened up:
The left hand panel untitled
is the coding panel, the top right has the SuperCollider documentation browser and the bottom right is the logs panel.
Reference
There is a guide to using the code panel (also known as the interpreter).