Jay

Turn the key on while holding the horn button. Do not continue to hold the key in the on position. The lift should start going through the start up sequence. The horn will sound shortly, release the horn switch then press it again quickly and release. Reading the first instructions, it sounds like you needed to hold the key switch while trying to get the horn steps completed. Just turn the key on as if you were starting the truck. The trick is releasing the horn button just after it goes off and flicking the horn switch again.