Well the rate of ascent/descent is controlled by the VS (Vertical Speed). In the radio panel you will see - or + indicating the descent or ascent.
If you change the number infront of the - or + it will increase the descend / ascent rate. However if you have a too high ascent rate, the speed will decrease very quidkly

if you need a screenshot showing this, just ask.
With the flight plan, grab a copy of
www.fsnavigator.com (30 free tries i think)
Welcome to Euroharmony