How to graph equation?

pick any set of values for x and compute y

Then plot the point (x,y)

You should recognize that this is a parabola, which intersects the x-axis at (0,0) and (-8,0)
The vertex is at (-4,-16)
If you plot those three points and draw a smooth curve through them, which gets steeper on the ends, you will see the shape.

Also, there are many handy online graphing web sites.
A good one is wolframalpha.com
Just type in your function, and it will show the graph, as well as many other useful bits of information.