Do I need to connect both the DVI cable and the 15-pin D-Sub cable of an LCD monitor to my desktop?

Recently bought an LCD monitor, but I confused by the instruction manual. I wonder if I need to connect the supplied cable at a time or simply choose to use either the cable 15-pin D-Sub or DVI cable.
Because it solves.

You only need to connect a cable. Either will work, but I recommend using the DVI cable the picture quality will be a little better.
If you do not have the DVI cable Just go with the 15-pin D-sub.