We've towed our 2007 Edge over 18,000 miles with no problems.
As AFChap said, DO NOT restrict the steering wheel in any manner.
Unless you have the keyless ignition, which I can't speak to, the sequence for the Edge is to put the gear selector in Neutral before turning off the engine. Then turn the key back as far as it will go (you won't be able to remove the key).
No need to do anything more other than install the auxiliary braking system (if you use a 'Brake in the box' system).
Bob (Squidly Down Under) & Peg - 2013 Ford Focus pushing a 2011 Phoenix Cruiser 2552S
"In God we trust" to preserve our country and bring our Troops safely home.
Carry on, regardless..................