Add a PAYRUN row by pressing the insert key in your PAYRUNS table, click the window select button below the PAYRUN window and select Pay List. Delete the employees from the Pay List that you do not wish to process and then process the Payrun.

The Payrun preview shows all the active employees you have chosen to process from your Pay List.

Yes, you would have to add another Payrun for the same pay period if you wish to process other employees not on your original Pay List (ones you have removed) above.