How to display events from .root files

Recently I download some dataA.root file from ATLAS open data set.

I tried to read data_A.3lep.root and display a list of events but I failed.

How could I read the events and select the events I am interested in from root command shell?

I know how to draw some basic histograms and select the events I am interested in, but I am kind of stuck with reading the file (first step).

Please read tips for efficient and successful posting and posting code

ROOT Version: 6.22/06
_Platform: Mac OS
_Compiler: gcc 4.2.1

Check out the examples and tutorials following the Documentation link above this page.
There are several ways; here is one example: