This guide will help you to make two types of stairs, i.e., a big and a small one. You must follow all steps in the guide to do so.
First, you will need two full-size logs and put them on the dotted lines as there is no support on the other side.
Now, go to the mid of the logs, and you will see an arrow; right-click, and the arrow will move in another direction. The leaning and upright arrows show ramps and stairs, respectively.
Then place the stairs.
After that, go inside to make the big stairs. Put the logs on the wall leaning to the ground and place the stairs in the same sequence by right-clicking.