Fellow Aviator
Depending on equipment installed (avionics) on the ADI (attitude director indicator) there is on the left the "speed tape" which provides indication of airspeed and in it, when you are for instance, accelerating, there will be an yellow arrow which is the "speed trend" which tells the speed at which you'll be in 10 seconds (it emanates from the speed you are at and indicates speed is changing). So, once you have the speed you want and you see that "speed trend" arrow indicating you are accelerating or decelerating you correct the throttle output by decreasing or increasing it as appropriate.
Very useful tool for maintaining airspeed, the speed trend.
You say that you never flew jets before. The people assessing you should help you. They will probably just want to assess you basic skills and not your knowledge of the aircraft. "First things first" Fly the aircraft and if you don't understand something that is occuring, don't be afraid to ask why is such thing happening.
Hope this was of help.
Best of luck,
Zerograv