How do i file tax for for arrears recieved

HI all, could any body please advise me with the following querry , thanks in advance:

My father is a retired defence employee, last year in nov he recieved his arrears of last 5 years from the 6 th pay commission, now he needs to file his returns , could you plaese guide me how will the income this year ?? will they be shown fresh this year or will he need to shoe the income in the previous years and edit the previous years returns forms, if so how will this be done?