Answer:
You take the X value and plug into the residual equation and find the estimated Y.
If the you have the points (20, 4) with the linear regression equation being y=0.138x+1.074, you would plug in X with 20 and solve. This means Y is 3.834. Then you subtract 4-3.834. This means the residual is 0.166. You would have to do this with all of the points on a scatterplot.