Prerequisites
The initial screen for maintaining a business partner depends on the Settings you have chosen for the initial screen leading into the business partner dialog.
For more information, see
Settings.Procedure
You are in the Business Partner dialog.
If a grouping has been defined as a standard grouping in Customizing, this grouping is chosen automatically. If you want to assign the business partner to a grouping that is different to the standard grouping, then you should select the grouping you require.
If you select a grouping with internal number assignment, you do not need to enter a business partner number. This is created automatically by the system.
If you select a grouping with external number assignment, you need to enter a business partner number.
Result
You have created a business partner in the role you selected.