I want to use turbo tax to file both federal and state returns for both of my full time college student children How do I do that ?

first, are you confident they need to file?  if their total income was less than the lesser of a) $12,200 or b) earned income + $350 and there were no tax withholdings, there is no requirement to file. 

@jheenan2  

@NCPERSON1 is correct. Once you've determined that your children should or have to file a tax return, create a new TurboTax online account for each of them. Never start another return by going back and overwriting everything in the return you just filed. This will replace your info, which means you won't be able to retrieve your return later.

To start another return in TurboTax Online, here’s what to do:

1. Sign out of TurboTax Online.
2. Select the TurboTax Online product you want to use for the second return and proceed.
3. On the Create your account screen, set up a new user ID for the second return.
   • You can reuse your email address if you want to receive e-file notifications for the second return.
   • Up to 5 accounts can be tied to the same email address.
4. After you've created the new account, you can start working on the second return.
5. If you can't create a new account because your web browser automatically logs you into your old account, you may need to clear your browser history, cache and cookies. Source: TurboTax FAQ

They may qualify to use one of our free products.

• TurboTax Free Edition, can be used by higher-income filers but only handles simple returns with no additional schedules.  Upgrades and add-ons, such as TurboTax PLUS and Audit Defense, are available.
• The IRS Free File Program delivered by TurboTax is geared towards lower-income filers, regardless of tax return complexity, and is only offered through the IRS Free File Alliance (FFA) program. No upgrades are available.

In the future, you might want to consider using one of our TurboTax CD\Download versions. The CD/Download product is a better value, as it allows you to e-file up to 5 federal returns (and prepare as many paper returns as you need) at no additional cost. To see a comparison of TurboTax Online versus CD\Download, click here. 

Related information: Do You Have to File an Income Tax Return?

You need a separate online account for each tax return you want to prepare, with a different user name and password.

You will pay a separate fee for each tax return unless they qualify to file for free.

For truly free tax returns, if the person’s income is less than $36,000, use the IRS FreeFile version of TurboTax.  This includes forms that the regular TurboTax would charge you extra for.  Free file is a separate website and you would need to make new accounts to use it. https://freefile.intuit.com/

or as explained, you may wish to use a CD or download product, which can prepare multiple returns without additional cost.