WWE 2K18

Here's what I did. I selected Play >> One on One >> Extreme Rules. Select your two wrestlers, I personally chose Vader for this one. When the match starts, go to the outside and press next to the steps to pick up the top segment of the steps. I did this in ring but I guess you could do it on the outside too. Go to your opponent and press any direction, and press & hold to lift up your opponent and carry them. Take them to the steps and press . This will slam them onto the steps. Be sure to press and not , as is the contextual slam. This in effect "recognises" that the steps are there and slams your opponent directly onto them.

I'd recommend picking up your opponent very close to the steps as I found any more than a few seconds of being carried and they broke out of it.