Start with placing a point at the y-intercept (0,3). Slope is equal to "rise over run", which is the change in y over the change in x. So the change in y is +3 and the change in x is +2. So from (0,3) go up 3 and to the right 2 and place another point. This should be at (2,6). Now do that again from the new point and place another point. You can do it again and again as much as you want. Now draw a line through the points. If done correctly, the line will be straight.