When you use the equation y=mx+b
y=y
m= slope
x = x
b= your y intercept
So you plug in your number and when you have done that you should have y=3x+-2
And then when you graph them on a coordinate plane you use RISE over RUN
Rise equals your y axis
Run equals your x axis,
So you start at the orgin, and go up 3 and then over -2.
Hope that helped