You need to e-verify or send the signed copy of ITR-V to the tax department after filing your tax return.
Search your inbox for an email from the Income Tax Department. Download it, print, sign and send it to the address mentioned in the document's last line.
The password to open the ITR-V is your PAN in lower letters followed by DOB (ddmmyyyy).
Instead of sending your ITRV, you can also verify your tax return online if 120 days have not been elapsed since you have filed the return.