You can usestaircase model or create your own staircase.

Method 1: Pre-made staircases can be found in the Library under Finishing—Stair Railings—Stairs.

Method 2: Make stair by ceiling custom on the wall

Method 3: Use free modeling to make stairs

详细教程请点击：https://www.aihouse.com/study/detail/Spiral-Stair-Design-(V5.0)-708