How do i apply 2018 over payment to 2019 taxes

You may need to upgrade to Deluxe to enter it.  If it didn't transfer over from last year then enter a refund from last year that you applied to this year here. BUT first make sure it's not already there. You don't want to apply it twice.
Federal Taxes
Deductions and Credits
Then scroll way down to Estimates and Other Taxes Paid
Other Income Taxes - Click the Start or Update button

Next page scroll down to 2018 Refund Applied to 2019
Click Start or Update by the tax you applied

To enter, change or delete a refund from the prior year applied to this years taxes (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 Other Income Taxes, click on the start or update button

On the next screen select the options under 2018 Refund Applied to 2019

Or enter refund applied to this year in the Search box located in the upper right of the program screen. Click on Jump to refund applied to this year

The prior year refund amount applied is shown on Schedule 3 Line 8 and on Form 1040 Line 18d