When Sean first came to us (almost 7 years old), he didn't know how to go up/down stairs. We taught him. He just had to have a "reason" to use them. We just kept encouraging and praising him whenever he managed to do it. Going up was much easier than down. He actually runs up the steps now.
He also couldn't get up on the bed. Instead of buying the steps, my husband made some. He took boxes (different sizes so he could make them like steps) and covered them with pieces of carpet. Sean went up them for about 2 days and then didn't use them. He figured out how to jump off the bed. Even now he makes a few attempts, at times, to get up on the bed. We keep a rug at the bottom of the bed so he has good traction for getting up/down.