Formula for slope-intercept is y = mx+b. The y-intercept is the point where the line crosses the y-axis. From there on, use the slope to graph the line. For example, if the equation is y = 5x - 2, you would want to plot (0,-2) first on the graph. Then, continue using the slope, which is 5. Slope is rise/run. In this case, you go up five, then to the right one, since there is always an invisible one if the slope is a whole number.
Hope that helped. :)