It can be done, my advice is to get some help because you said you " never flown, an aircraft engine and JR X-378 controls"

You need to change the mode to mode 2 (I assume) in the "System Set-Up Mode"

Press and hold the 'down' and 'channel' buttons together, and turn the 378 on, then release the down and channel keys. Press the 'down' button until you get to 'stick',

Now press the + or – keys until you see 2.
Then press the 'down' and 'channel' buttons together again.

Turn off the transmitter, remove the crystal & battery, and open the transmitter case on the back, and change the ratchet and spring on the elevator stick to throttle stick.

Hope that helps, but please check with an experienced modeler!

Regards, Gert