Create a custom shape stair with a fill and lines. Draw the shape of the stairs with the fill tool and then use the line tool to draw the path. Select the fill and lines and go to Design > Design Extras > Create Stair Using Selection
There are 5 different Ladder / Access Stairs in the ArchiCAD Library that are great for fitting out plant rooms and industrial projects.
Generally we place a stair on the story where it starts (Home Story), and we want it to show on the story that it finishes on (One Story Up). Within the Stair settings goto Floor Plan and Section > FLOOR PLAN DISPLAY and set Show on Stories to Home & One Story Up.