I'm trying to file my latest W2, but I'm not getting the option to do so

What do you mean by "latest"  W-2?   If you already e-filed without that one, you messed up your tax return.  Now you have to wait for your original return to be fully processed and then file an amended return.  You were supposed to put ALL of your W-2's on the same tax return.

The 1040X becomes available late in February, so you have to wait for it.  If your return is still being processed now, it would not be a good idea to amend yet anyhow.  Sending in an amended return while they are still processing your original return could cause confusion that would delay your refund for months.

Check back later for the 1040X.   AFTER your return has been fully processed.

How do I amend my 2019 TurboTax Online return?

A 1040X cannot be e-filed.  It must be printed and mailed.  It will take about 4 months for the IRS to process an amended return.  It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.

Wait about 3 weeks from mailing and you can check the status of your amended return:

https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1

https://www.irs.gov/filing/individuals/amended-returns-form-1040-x/amended-return-frequently-asked-questions

https://ttlc.intuit.com/questions/1908543-do-i-need-to-amend

https://ttlc.intuit.com/questions/3318997-how-does-the-refund-math-work-on-amendments