Visibility Settings:
The visibility settings (whether or not to include planet lines) are found on the first two tabs of the Graphic Ephemeris Options window and are a series of checkboxes (one for each planet):
The Natal Planets tab include checkboxes for natal positions that you want included in the graph. The Transiting Planets tab has the same, but for the planets you want shown as transits. Unless you are running a graph for a short period of time (say 2 months or less), it is best not to include the position of the Moon, because the Moon moves so quickly that the graph will be full of lines for the Moon. It is a good idea to keep the time scale in mind when deciding whether to include a planet in the graph. If the graph spans 10 years, then it is probably best to ignore the Sun, Mercury, Venus and the Moon (leave unchecked).