I've not done it, or even seen it, but if I remember correctly, you remove the mattress, lift the head of the bed up to reveal the limit switch and remove the yellow wires on each side of the limit switch and connect them together.
I think Yellow is WBGO's wire color for 12v positive wiring. The switch completes the circuit hence when you bypass the switch and connect the two wires together you can operate the bed slide.
MIND YOU!! I'm going on memory here so my wife would tell you to not believe a word of this description.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad