A taxpayer gets Password and PIN when he completes first part of the Registration process. 

However, he cannot start any task or file tax return unless he completes second part of the Registration process by submitting the Form of Registration after completing data entry and attaching the required documents.

Once Registration Process is completed, you can file your tax return or create any task on Iris. 

So fill and submit the form of registration so that you can continue to file your return for the year.

Source: fbr.gov.pk