To create a staircase, go to the Floorplan mode, and click on the Stair icon in the Architecture ribbon. One you are in staircase creation mode, go to the lefthand properties panel.

There, under Modes, you can select the staircase type, side from which to draw the staircase, and whether to draw a step or a ramp, by selecting from the drop-down menus under Drawing Mode, Drawing Side and Step Type fields respectively. Under Default Dimensions in the left panel, you can determine the measurements of the staircase such as maximum height, width of step, tread depth, riser height, landing height and offset, by selecting the desired option from the corresponding drop-down menus.

All these properties can be edited even after creating the staircase

Next, to draw the staircase, ensure you are still in creation mode. Then, click once on the point from which you want the flight to start. As you move your mouse, the flight of steps gets formed in that direction until you click on another point to end the flight. In the case of a staircase with two or more connected flights, click along the points that form the path of the overall staircase.