Can someone explain the penalty for "not paying enough taxes during the year"? This has never happened before. How can this be since taxes are not due yet?

That is explained here. 

https://www.irs.gov/taxtopics/tc306

Thank you very much.  This was a total surprise to me and I do not understand what one must do to avoid that, as this has never happened to me before.  

The IRS says:

Taxes must be paid as you earn or receive income during the year, either through withholding or estimated tax payments.

If you do not pay enough during the year through withholding or estimated tax, you will be assessed an underpayment penalty.

Please read this IRS document for more information.

How should one submit those estimated payments and why did turbotax not so advise?

Explained here. 

https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes

TurboTax will generate estimated tax voucher for you. 

They did not do that for me and I have to say, i am pissed!  

If you haven't yet filed your return, you have the option to go to the Underpayment Penalty section in TurboTax and answer the interview questions in case your situation is one in which the penalty can be reduced or eliminated; for example, if you were in a Federally declared disaster area during a specified time.

If TurboTax is showing an underpayment penalty on your return, visit or revisit the Underpayment Penalty section under Other Tax Situations and answer the interview questions. The penalty calculation may change based on your answers, including information about when your withholding was applied. In addition, if you believe you qualify for a waiver of the penalty, you can request a waiver in that section.

The IRS may reduce an underpayment penalty if any of the following apply:

• You or your spouse (if you file a joint return) retired in the past 2 years after reaching age 62 or became disabled and you had reasonable cause to underpay or pay your estimated tax late. See Waiver of Penalty in Instructions for Form 2210PDF.
• You had most of your income tax withheld early in the year instead of spreading it equally through the year. 
• Your income varies during the year. Complete Form 2210, Schedule AI, Annualized Income Installment Method PDF(found within the form).

The penalty for underpayment of estimated tax can also be removed to the extent that the underpayment is the result of a casualty, local disaster, or other unusual circumstance such that it would not be fair to impose the penalty.

See here for information about different TurboTax tools you can use to calculate withholding and estimated taxes

See this IRS webpage for more information.

If your income is from wages, you can change your W-4 to deduct more taxes this year if needed. If your income is from businesses or other sources, you can have TurboTax complete quarterly estimated tax vouchers. Do this in the Estimated Taxes section of TurboTax. 

@EF130

thank you.  All this is new to me; I can see I was uninformed.