To create a road, right click on the hex where the road is to begin. In this example, the road will be a continuation of a previously existing road

Then, left click to the hex the road will extended to

Continue to left click to new hexes until the road is complete

To turn off the road drawing, just left click on a non-adjacent hex

To erase a road, right click on the hex where the road to be erased is.

Then, left click to the next hex along the road you want to erase