After you file

Normally, if the penalty is shown on the form 1040, then it's already added into what you owed to the IRS and "should" already be part of your scheduled payment. 

 

IF it turns out that it was not included, the IRS will send you a bill later for it.

 

____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*