Beautiful, thanks so much - To be clear this is just for estimating the quarterly taxes I will have to make for 2018, but it is up to me (not via TurboTax) to directly pay these taxes to IRS?

Yes.  You either mail in the 1040ES slip with a check or you can pay Online at
<a rel="nofollow" target="_blank" href="Https://www.irs.gov/payments">Https://www.irs.gov/payments</a>

TurboTax can compute these for you, as described in the FAQ below.  It's possible that you can be penalized for underpaying estimated taxes, but not for overpaying.

 https://ttlc.intuit.com/replies/3301730 

If you're more comfortable computing estimated taxes yourself, please see this IRS page on Estimated Taxes, and 2017 Form 1040-ES, Estimated Tax for Individuals. 

Thank you, some more questions, first where is this "Review Your Estimates for 2018 screen" you referred to?

When paying out estimated taxes for 2018, when it comes around to file taxes for 2018, where in the Turbo Tax application can I declare how much in taxes I already paid?

If I underpaid, how much do I have to underpay to get fined?

If I overpaid, how do I reclaim the money I overpaid?

If you overpay you get a refund on your tax return same as now.  It all is combined on your return.  

To prepare estimates for next year you need to be in your  current return.  You can just type W4 in the search box at the top of your return , click on Find. Then Click on Jump To and it will take you to the estimated tax payments section. Say no to changing your W-4 and the next screen will start the estimated taxes section.

OR go to
Federal on left
Other Tax Situations
Other Tax Forms
Form W-4 and Estimated Taxes - Click the Start or Update button

When you get to the W4 and Estimated Taxes section, say you want to adjust your income to go though all the screens.

you don't have to pay four times a year. If you get a burst of income, make an estimated tax payment ( 10%,12%, 15%, whatever)  any time at www.irs.gov/directpay.