Hello and thank you for your question.
You can request a copy of your return from the IRS if TurboTax isn't producing. If TurboTax is showing different prior year amounts than what you actually had, then perhaps you started online but were forced to finish using a desktop version of TurboTax's software (this happens a lot because the online version of their software is junk compared to the desktop version, which is still junk, and many times they will have you switch to the desktop version to solve problems). Aside from that, it's possible that TurboTax's software has not properly transferred prior year information.
How much is your time worth? Chances are this is a simple 1040 return to any tax pro that you could have amended for $100 or so. You've spent 24 hours...
The online version of TurboTax cannot be used to amend a 2014 return. You'll have to download their desktop software to do it. You'll also have to download your tax file from their website if you filed online in 2014. Then you'll have to open the software and after you've opened the software, use the software to open your tax file (ie... you can't just open the tax file you've downloaded). From there, you'll need to make sure the numbers match exactly with what you originally filed (both fed and state) before you can start the process of amending your return. Once the numbers match, you indicate that you are amending and proceed to make changes. Form 1040X and whatever state form you need should populate. So, if you have yet to even get your tax file open, then unfortunately after 24 hours the hardest part is yet to come.
Now for some good news: you aren't really accruing much more in the way of interest and penalties. Relax. Being understandably frustrated and feeling rushed to get your taxes done will not help. It's a recipe for making even more mistakes.
TurboTax is good for simple returns, but not for anything complicated which, if you've never amended a return before, probably includes amending your return. Just like buying a set of tools won't turn me into a mechanic, buying TurboTax won't turn you into a tax pro (despite what Intuit might imply in its advertising...). Again, I strongly suggest you just get someone that knows what they are doing to amend it.
If not, you can always call TurboTax. They do have a support team there waiting to help which may or may not cost you extra to make use of. If you're lucky you'll get one of their "tax advice agents" instead of one of their "tax support reps." The advice agents are credentialed (either EAs or CPAs) that can try to painstaking walk you through everything over the phone. If need be, you can set up a screen share so they can view your computer screen... don't try this on a cell phone or tablet (that's nuts!!!). If you're even luckier, that will work, because they aren't computer professionals and won't be of much help if you can't get the file downloaded, can't do a screen-share because of some firewall or other computer settings, etc.
Additionally, I suggest you compare the refunds you received with your original returns to make sure the IRS or state didn't take the liberty of correcting something for you prior to releasing your refund. They'd send a notice if they did, but I've seen plenty of times where this has happened and people don't realize it and for some reason that notice just doesn't ring a bell. Amending your return is much more complex after the government has changed something, fyi.
Alright, good luck! That's about the most I can do for you on a written JustAnswers response. I suggest you get a tax pro to help and save yourself any more grief.