Try this, Since you have already filed (if your return was already accepted), to get back in, sign into your account.
Select Tax Home in the left menu.
Scroll down to Your tax returns & documents.
Select 2018, and then select Add a State (you're not actually adding a state, this just gets you into the right menu).
Go to Federal taxes (or Personal) -> Click Deductions and Credits (choose option to work on your own) -> Scroll down to Estimates and Other Taxes Paid -> Choose Income Taxes -> Scroll to Payments with Extension ->
