there are videos on youtube about installing and configuring GNS3. why read if u can watch it. right.
IOS for GNS3 is the problem. you suppose to be using IOS you already have or own (from real router); although I am not sure how is that legal. Problem is that there is no IOS for GNS3, no demo, no student version, etc.
Still, somehow people get it and use it.