I made four pre-payments of $607 each [total = $2428]. where do i record this?

To enter the Estimated Tax payments made for 2018.

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