How do I set up BBQ to rotisserie

"I have never used my rotisserie and I would very much like to. I have a Propane BBQ with one rotisserie burner located at the back, and two burners on the bottom. This BBQ has lava rocks. I am clear about balancing food ont the rod, etc. but how do I set up the rocks, drip pan, pre-heat, and do I only use the rotisserie burner and no heat from below? Please help. Thank you."

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