When my husband built one, he bought plywood at the home improvement store and took it to their ready made stairs and TRACED the one he wanted to make. THen he took the wood home and cut it out and copied what he saw and photo copied with his phone camera. He built our two sets of steps from that. I hope this helps.
If inside, that is almost an art form that includes handrails, but a simple one could be seen on you tube video tutorials. Start there until you find the type that fits your project. Good luck and have fun.
Before you build, here is the Building & Safety Codes for your planning purposes.
This will also help you visualize how to build the staircase.
hometalk has some ideas!
This tutorial may help: https://do-daddy.com/how-to-replace-carpet-stairs-with-wood/
Hope this Helps! Jeremy - https://do-daddy.com