If you have a 2014, you probably have the older style remote. On my 2015 351RSTS, I found the button on a board mounted behind the panel in the storage area. There's a small yellow light in the lower right corner with a small black button adjacent to it. Press the black button until the yellow light blinks. Press the ON/OFF button on the remote until the light goes solid yellow and you're done.
Mike, Sue, Sissy and Little Man
2015 Ford F350 Lariat FX4 6.7 CC DRW
2015 Eagle Premier 351RSTS