The lift select button is on the left handle.
Same place as the horn button on the right handle.

I didn't read your post properly. Your truck is operational so all that needs to happen is a configuration download as I described.
Hold both deadman down. Key on with right hand and use left to push lift select 3 or 4 times before the truck starts selftest. Some guys just keep pushing the button fast. There is some timing to it but it's not like the pedal dance on a cat or anything.
You'll get it.