To graph $y = -g(x)$, reflect the original graph of $y=g(x)$ across the x-axis. The points (1,0), (2,4), and (4,0) become (1,0), (2,-4), and (4,0).
To graph $y = -g(x) + 4$, shift the graph of $y = -g(x)$ up by 4 units. The key points (1,0), (2,-4), and (4,0) become (1,4), (2,0), and (4,4).