Use slope intercept form:
m is the slope.
b is the y-intercept.
Your y-intercept is only the y value in your point (0,2), which is 2. We don't need the x value because it is understood that it will be 0 because the x-value at the y-axis is always 0 (think of the typical graph).
Just plug in (-2/5) for m and 2 for b
To graph, place a point at the y-cept: (0,2) and, using the rise over run method, place a point 2 down and 5 to the right of the point. Then connect the points. I've included a picture.