Remark
That's an excellent question. There are programs on the internet that have all kinds of graphing abilities. The simplest one is Desmos. Below is the answer to your question. Your graph is blue.
The family of graphs begins with y = 2^2 this is the point 4. Notice that with the y there, there is a horizontal line going through (0,4)
The red line is y= 4
The blue line is y= 5*(2)^2 which is 20
So the blue line is a horizontal line going through (0,20). That's the graph you want.
The green line is just one I added to show you what happens when add or subtract something from 20. I choose 6.
y = 5*2^2 - 6
Notice that gives you a line of y = 14