This instructable helps you to download Arduino Software (Arduino IDE) for Windows, Linux, Mac OS.
Following steps helps you in downloading the Arduino Software
Step1: Type Arduino in Google
Step2 : Select Download tab in Arduino Website.
Step3: Download the Software by clicking the related links (EX: Windows, Linux, Mac OS)
Step4: Click on Just Download.
After you completed downloading the Arduino Software, Install it and use it for your projects.
For Basic LED programming refer below link.