Here is a tutorial that may help.
Here is a helpful video: https://www.youtube.com/watch?v=iALK0-n-81c
This might be something to have a contractor for. Though these tutorials are very helpful.
Yes, Staircases have both health and safety codes for many reasons.
Here’s a Code-mandated stair requirements “over view” to get you familiar with how to cost-effectively hire a qualified helper.
how do I turn my attic into a bonus room