Make a table of points by choosing values for the x-coordinate.
Then substitute each into the equation y=x²-4 to find the value
for the y-coordinate:
 

 x  y=x²-4  point
-4    12    (-4,12)
-3     5    (-3,5)
-2     0    (-2,0)
-1    -3    (-1,-3)
 0    -4    (-0,-4)
 1    -3    (1,-3)
 2     0    (2,0)
 3     5    (3,5)
 4    12    (4,12)

Plot all those points:

  

Sketch in the graph:

  

Edwin