We have stairs out the back and taught both girls and grandsons how to use them as soon as they could crawl. Taught them to go down feet first, backwards, and come up the same way hands first. The first few times I walked behind or in front until they got the idea. It won't take them long to learn.
It got a bit nerve wracking when they wanted to walk down but I made them hold onto the rail or they had to go down on their hands and knees