Regarding the stairs: in Punch you should draw the stairs from the lower level to the upper level. So, just insert your stairs in the basement--> set the stairs with the same elevation of the basement floor--> they will go from the basement to the first level
To calculate the stairs--> (in inches-->first floor elevation - basement floor elevation) / 7" ==> this will give you the number of steps. Then, the number of steps x 10" ==> length of the staircase. These dims are just for estimation and vary depending shape, codes, etc

Let us know if you need additional help

Patricia