The graph for the linear equation 'y = 3x + 1' is a straight line.

Thus, we only need two points from the line to plot.

For 'x =0' we get 

y = 3*0 + 1

y = 1

One point from on line is (0, 1).

For 'y = 0' we get

0 = 3x + 1

x = -1/3

Second point on the line is (-1/3, 0).

Now, we can plot the graph by drawing line that goes trough (0, 1) and (-1/3, 0):