Sketch1, 3 and 6 are not constrained. I would start here -
http://home.pct.edu/~jmather/AU2007/MA105-1L%20Mather.pdf
Is this a school assignment?
After going through the above link I would then go through these tutorials
http://home.pct.edu/~jmather/content/DSG322/inventor_surface_tutorials.htm
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