The following pages describe how to use CGAL on different environments:

Using CGAL on Unix (Linux, macOS, ...)
Using CGAL on Windows (with Visual C++)
Essential and Optional Third Party Dependencies gives information (supported versions, download links) of the required and optional third party libraries.
How to use CGAL with CMake explains how to use CMake to link a program with CGAL.

The following pages cover advanced installation options:

Summary of CGAL's Configuration Variables gives information about which CMake variables can be used to help resolve missing dependencies while using the cmake command line tool.
Building CGAL libraries (non header-only mode) describes the deprecated process of configuring and building CGAL.

The following pages cover the structure of the manual and general information about CGAL:

Organization of the Manual gives an idea of where you should look for documentation.
General Information lists how to control inlining, thread safety, code deprecation, checking of pre- and postconditions, how to alter the failure behavior, and how to check the version of CGAL.
License describes the different licenses used within CGAL, with which users must comply.

Once you are familiar with building your programs with CGAL and how the documentation is structured, you can head over to the Tutorials for a gentle introduction to CGAL, or directly to the package(s) that interest you the Package Overview. Each package contains simple examples of the various functionalities of the package.