Is it possible to add fastai library to path or environment variable so that i can use it from any location/path in my computer?
Sure, this is a Python problem. Probably the best way to do it is to set your PYTHONPATH environment variable. Probably something like this:
See that fastai is the cloned repository, your fastai module shoud be inside it.
See the PYTHOPATH documentation.
StackOverflow is great to answer this kind of questions.