Already filed return, do I need to pay estimated tax penalty separately?

[miniwrite]

First year with self-employment income. In 2017 I calculated that I didn't owe estimated payments b/c I wasn't making very much through self-employment. However, TurboTax says I owe a few bucks in line 79. But I already filed my return and it doesn't seem TurboTax included this amount with my federal balance due. Why not, and how do I pay it now?

[miniwrite · Accepted solution]

*Nvm answered it myself. Turns out the instructions for 1040 have you go backwards and add in the amount from line 79 to line 78, so I did pay it.