You can start with learning the fret board. Learn the natural notes (A, B, C, D, E, F & G) on the 6th. and 5th. strings to start. These are your "root notes".
Look here...
http://www.justinguitar.com/en/TB-007-NotesOnNeck.php
And here...
http://www.justinguitar.com/en/BC-172-G5-powerchord.php
Here he's showing you "power chords" or "fifth chords", basically half of
a barre chord. Once you're able to identify and play the fifth chords work on playing the full barre chord.
The other notes not shown/listed on the "Notes on Neck" diagram are sharps/flats. They're called "accidentals".
Here's some info...
http://www.justinguitar.com/en/TB-006-NoteCircle.php
and...
Justin has some great lessons for free. You should take a look.
www.justinguitar.com
http://www.justinguitar.com/en/BC-00...nersCourse.php
Justine's website should keep you busy for a while.