dotted lines
Go to your right, where your swatches, layer palette, etc, is located. On the side, there are a few buttons. Hit the Brushes button.
Hit brush tip shape.
Select the size brush you want to use. I'll be using 3px.
Change the Spacing to 176%. It should look something like this in the end.
Now, use the brush tool to draw, add a design to something you were making, etc. This is how mine came out:
Hope yours came out the way you wanted it to !