Remember there are several ways to go about graphing a line.
From the equation you can plot the y-intercept and use the slope to find another point on the line.
For example, for the equation y = 2x + 4, the y-intercept if 4 and the slope is 2. Plot a point at (0,4) and use the slope to move up 2 and to the right 1 and plot another point at (1,6). Now draw a line through the points.
You can also find both intercepts by putting 0 in for x and then 0 in for y. Using the equation above, you get 0 = 2x + 4, therefore x = -2. The x-intercept is -2, so plot a point at (-2,0). Putting a 0 in for x we get y = 2(0) + 4, so the y-intercept is (0,4). Plot that point and draw a line through the points.
You can also pick any 2 values for x and find the corresponding y values. For y = 2x +4, suppose we pick 1 for x, therefore y = 6. Now pick x =2 and you get y = 8. Plot points at (1,6) and (2,8) and draw a line through the points.