How can I learn to read and understand all the cool stuff on the blackboards in a science documentary, like Nova from PBS(Public Broadcasting Station) ?

Take notes while viewing.

Then treat your notes as as a research project. Start with item number one. Take your time. The internet is the most amazing library of all time.

None of us, even the most pedantically over-educated, understands all the nuanced experiments and discussions on Nova. Neither does David Pogue, who is often the intrepid narrator and guinea pig. During a wonderful program on food and nutrition, for example, he eats some pretty weird stuff to make the program interesting.

Maybe enroll in an online college?

Gerard ‘t Hooft has compiled a notional ciriculum and links to resources for the autodidacts out there wanting to become theoretical physicists. This is a much more ambitious aim than yours, though the lower level material listed there might be of interest to you.

Physics books pitched at general readers which I recommend:
The Cosmic Code by Heinz Pagels (best layman’s account of relativity that I have come across)
The Second Creation by Crease and Mann (historical account of particle physics)
The Inflationary Universe by Alan Guth (the development of big bang cosmology and its tie into particle physics)

If these have whetted your appetite for more then you might want to dig into…
The Road to Reality by Roger Penrose
Be warned this one will require very serious study and a long, long time to work through completely.

There’s also a new book out by Leonard Susskind entitled The Theoretical Minimum. There’s also a website for it, and it sounds like you might appreciate it…

“A number of years ago I became aware of the large number of physics enthusiasts out there who have no venue to learn modern physics and cosmology. Fat advanced textbooks are not suitable to people who have no teacher to ask questions of, and the popular literature does not go deeply enough to satisfy these curious people. So I started a series of courses on modern physics at Stanford University where I am a professor of physics. The courses are specifically aimed at people who know, or once knew, a bit of algebra and calculus, but are more or less beginners.”