Where is my blind spot?

Where exactly is it? I am a new driver and the road from home to work is extremely busy, 5 lanes. sometimes to get into the left lane, I first indicate, check the rear view and side mirrors but just as i am about to switch lanes, there's a car hooting at me and is right in the lane i want to go in!! I don't know where this blind spot is and it makes me very nervous :'(