On JR X-378 you must be in AIL channel for the left aileron and AUX1 channel for the right wing

Then with the radio off, hold the "channel" and "down" buttons and turn on the radio which will put the radio into system mode. Use the up or down keys to get to the "wing" section that will show in the upper left corner. Now use the plus or minus keys to get to "FLPER" which is flaperon mode.

Now move the sticks to be sure the ailerons move. If they both move in the same direction you will need to reverse either one of the channels, the aileron channels is probably the better and easier of the 2 to change. Once you have that then just exit the wing menu and turn the radio off then back on and test it.