I believe while it’s important to have dangerous areas of the house properly gated or blocked off from little people, it’s also important to take time to familiarise your growing baby with these areas of the house, to eventually be able to be independent through all areas of the house (of course this is only when and where appropriate, every house and child is different, so the risks and dangers differ from home to home. Use your own judgement when making these decisions)
When baby is starting to crawl and pull up take them onto the stairs and sit one step below them, and encourage them to climb up the stairs. This is a good activity on a rainy day if baby has lots of energy to burn and nowhere to do so, as well as to prepare baby for being able to safely navigate on stairs.
If baby tries to come down the stairs gently encourage them to turn around to go back backwards on their belly reaching out with their feet. Though some babies and toddlers struggle with this, some toddlers will only want to go down walking forwards in which case you may want to encourage them to hold the railing as they descend.
Remember, this is just baby steps, don’t expect them to learn how to safely go up and down stairs until they are at least a couple of years old, but the more they practise the easier it will be when the time comes.