I have a blueprint of BMW M6 and i would to design it from the scratch and in a simple way. There are lots of tutorials in YouTube which is very confusing and they don't try to explain properly.
Please help me out.
There are MANY steps to modeling a car in SolidWorks.
Most important is your initial scaling and layout of the reference sketches.
After that, you'll be wearing out the spline sketching tools, Projected Curve tool, and most of the Surfacing tools.
Are there specific parts of a specific video you did not understand? With more specific questions, it may be possible to better address your question.
I believe there is/was an Audi A8 tutorial put out some years back. If you can find a copy of it, I heard good things about it.
You might also download some similar models from this site and study how they were created.
It is not a car, but my Striker Dive Bomber model is based upon blueprint like images. DMB-87 Quick Decent Dive Bomber: Striker
You might also review the SolidWorks Surfacing Bible which was written by Matt Lombard. It has some good tutorials in it which cover many of the skills required.
Splines, Projected Curves, and Boundary Surfaces are going to be your new best friends!