Template to Draw Supply Demand Diagrams

So I like to use technology in class (can you tell?!) and want to be able to draw my supply/demand curves digitally.  So here Creately has a template for supply demand graphing. The only thing I can't figure out is how to draw a curved line. You can draw a line from one point to another and then click in the middle and drag the small square backward or forwards and then click on either side of the middle and click again in the middle to get a picture such as I have below.  Keep with this blog and I will find a way to do it a little easier.