Nothing difficult if salary is the only source of income and you have white money in your assets.
First you need to get register on FBR IRIS system
Then enroll yourself on FBR IRIS System
You will get username ( cnic no) and password..
After that you need to fill two forms
1- income tax filed voluntary for complete year
2- statement of assets and liabilities filed voluntary for complete year.
In number 1 you need to write your total salary and tax deducted for a year
In number 2 you need to declare what asset you have in term of bank account, cash, property, vehicle etc.
And expenses in year
In final reconcoiled amount should be 0