The way to <b>access documentation</b> of any program or package is
to enter <u><tt>man <i>program_name</i></tt></u> in the terminal.

For instance, to read the documentation of the <tt>man</tt> program, the
reference manual viewer, you would enter: <u><tt>man man</tt></u>. You exit <tt>man</tt>
with the 'q' key.

Additionally, the short help of a program is, by common GNU
convention, accessible with <tt>--help</tt> switch, e.g. by typing
<u><tt>man --help</tt></u>.