When you open the procedure, the Create tab first appears. In the upper portion of the tab you classify and select the list.
In the lower portion you select a period as the planning horizon for the requirement calculation.
At the bottom of the tab you will find settings under the headings Show..., Order types, Level and Part types.
Once the list has been loaded, you can modify many of the settings you selected under the Create tab, by right-clicking in the list and opening the Info menu.