The first requirement is to identify the employees for whom the new payment is to be created. If it is possible, then a HR Query can be written and the output exported to a CSV file (Note: this file will only need to output the employee number, though you may want other fields in order to check that the query has returned the expected employees).
If it is not possible to create the CSV from a HR Query, then it could be manually created or created from some other date that you have available.
You will then need to format the CSV file, with the heading line and columns that are required to create a fixed input record.
The employee number will need a column heading of emp_id.
You will need a column headed payroll_id to hold the payroll code.
You will need a column heading of type_id, which should be set to A to force the payments to come in each period.
You will need a column heading of def_value to hold the payment value.
You can optionally have columns start_period and end_period if you wish to limit the range of periods when the payments is to be made.
If this file is imported via the work bench to the fixed payments file, then both the fixed payments and working file will be updated.