While I am still not 100% sure what you are trying to train this is how I would train what I
think you are trying to train

.
I tend to use "paws" or "paws up" for placing both front paws on an object, then "off" or "back off" for stepping down. My dog has generalised these so I can point to just about any object and cue "Paws up". So to teach him to close the door I simply cued "Close the door - paws up" until he associated the cue close the door with the action he was going to be told to do next, or for beginning pivoting I cued "paws up" onto a book then shaped/lured the pivot. For me "Back off" tends to be more ragged in it's execution because I've never formalised it - and it is different for different objects.
In your case why not use a low stool, a thick book, or maybe the bottom step of your stairs and either shape or lure front paws on - I used luring and patting the object encouragingly because I'd not really heard of shaping when I taught this. If your dog knows "back up" you can then cue "back up" or "reverse" or whatever to get him to step back off the object. If your dog doesn't know back up just let us know and we can help you with that.
If you use the bottom step of your stairs you can then introduce him to the idea of you being alongside him as he steps on and off.