Can I file my second w2 after I have already filed the first w2

You will have to amend the original tax return to add the 2020 W-2

If the return is accepted you will have to amend your original tax return. An amended return, Form 1040X, can only be printed and mailed to the IRS if the original tax return was not e-filed. The IRS will take up to 16 weeks or longer to process an amended tax return.

Before starting to amend the tax return, wait for the tax refund to be received or the taxes due to be paid and processed by the IRS.

See this TurboTax support FAQ on amending a tax return originally completed and filed using the 2020 TurboTax online editions - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/01/27577

The IRS Form 1040-X for amending a 2020 tax return is scheduled to be available on 03/25/2021 (subject to change)

ALL your income was supposed to be reported on the ONE tax return you file each year.   NOW you will have to wait until the IRS fully processed your original return and you have the original refund in hand then, and only then can you amend the return.

Some quick ground rules:

1. Be sure the original return was filed and accepted.
2. DO NOT go back into the return or change anything before you start the amendment process.
3. Gather everything you need before you start.
4. Complete the entire amendment process before you log out.
5. Starting with 2020 tax returns you can E-File a 1040-X amended tax return.  The 1040X will not be functional until 3/25 at the earliest. 

 You can correct a return that you've already filed and had accepted.  Select the year that applies and use this guide to proceed.

Select your tax year for amending instructions:

• 2020
• 2019
• 2018
• 2017

For additional information please refer to  How to Amend