How to add parameters in application front end for below code

For the below code snippet,we need to make the reverse flag and period code as input parameters.Currently below script is not generating data file on WD+0 because of period selection.The file generated by below script will feed to gl listener program to generate JV's.The field mappings with gl interface tables are as below.How to make  Reverse period/Flag as input Parameter?

reference6

VARCHAR2

100

Journal Ref

        ||'|'||NULL

reference7

VARCHAR2

100

Journal Rev Flag

        ||'|'||NULL

reference8

VARCHAR2

100

Journal Rev Period

        ||'|'||NULL

        ||'|'||'Y'

        ||'|'||b.period_name 

        ||'|'||'N'