Salary Return

You mean to say Income Tax return ?.

Due date for Filing income tax return for F.Y 2019-20 is 30th November, 2020

You can file your income tax return online on incometaxefiling website after Login with your credentials.
If you have Income from Salaries, One House Property only, Other Sources (Interest etc.) than you can file form ITR 1.

In income tax return, we have to disclose all our income (like salary, house rent income, interest income, capital gain, business income) earned /accrued or deemed to earned/accrued during the relevant financial year in relevant forms Notified.

U can field online itr1

It is not that easy that can be quoted in a message , I will suggest you one app that guides you to calculate your own return....
......it's an app called my tax app