what specific part are you trying to use?
What you want to do is see if the part you want is in the Diptrace library. If not, it's a simple matter to make your own library, and make your own component.
Simply copy their component gate to your own library. Then in your library, add a part. The part is just a box with VCC and GND pins (trust me...it's more convenient to make it a separate part in the long run than to hang it off the gate). Then attach the pattern, and you're done. It's just a few minutes worth of work..maybe a 1/2 hour the first time.