You do not File for the stimulus package since the stimulus package has not even been passed by Congress or signed by the President into law. Wait and there will be more information later after passage.
They said for people who recieve social security should file for the stimulus check
The details of the Stimulus payments has not been worked out just yet. Once things are finalized we will be able to provide more guidance. In the meantime, you can visit the following links for the most recent updates:
Economic impact payments: What you need to know
TurboTax Corona Virus Tax Center Updates
You don't need to sign up for the stimulus package. The government will be able to leverage the direct deposit information in your 2019 tax return to deposit these stimulus funds electronically into your account.