I forgot to add state taxes i paid in 2018

[1a]

my retirement check does not take out state taxes I pay it  myself and did not enclude that amount in my returns

[MichaelL1]

To enter estimated taxes paid (Federal, State, Local)

•    Click on Federal Taxes (Personal using Home and Business)
•    Click on Deductions and Credits
•    Click on I'll choose what I work on (if shown)
•    Scroll down to Estimates and Other Taxes Paid
•    On Estimates, click on the start or update button

[MichaelL1]

If you already filed the State should catch this and give you credit to the state taxes paid.  If not then you will need to Amend the state return.