To download NetBeans IDE just visit the NetBeans site and download the proper version of the IDE based on your OS, Architecture and technologies. You can select from the following technologies:
Java SE. Supports all standard Java SE development features as well as support for NetBeans Platform development and JavaFX 2.2 SDK (or newer) or JavaFX 8 SDK.
Java EE. Provides tools for developing Java SE and Java EE applications as well as support for NetBeans Platform development and JavaFX 2.2 SDK (or newer) or JavaFX 8 SDK. This download option also includes GlassFish Server Open Source Edition 4.1.1, and Apache Tomcat 8.0.27 software.
HTML5/JavaScript. Provides tools for HTML5/Javascript development. Includes Java Runtime Environment and does not require a separate Java installation.
PHP. Provides tools for PHP 5.x development, Zend and Symfony Framework support. Includes Java Runtime Environment and does not require a separate Java installation.
C/C++. Supports development in the C, C++, Qt, Fortran and Assembly languages. Includes Java Runtime Environment and does not require a separate Java installation.
All. This is a full download option, which contains all the runtimes and technologies available for the NetBeans IDE.
The size of the installer varies per OS and also by technologies selected. Java JDK is required to be installed in your computer. As an option you can also download the JDK bundled with NetBeans IDE.
After installation you can also remove or add technologies in the IDE's Update Center.