Turbo Tax online is only good for 2016 returns now. You have to buy and download and install the prior year Desktop program to do an older return. There is no penalty if you are getting a refund. You have to mail in past year returns. You should just ignore what you entered in the Online version. You need to start over in the Desktop program. You can buy the prior year programs here,
https://turbotax.intuit.com/personal-taxes/past-years-products Then you can still use your Online account to do this year's 2016 return but you will need to clear out your entries and start over for 2016. Or abandon this online account and start a new one.
https://ttlc.intuit.com/questions/2586254-using-clear-start-over-in-turbotax-online If you want to do 2015 for free you can get the blank forms from the IRS and filll them out by hand. Here are some blank forms & instructions for 2015
1040
https://www.irs.gov/pub/irs-prior/f1040--2015.pdf Instructions
https://www.irs.gov/pub/irs-prior/i1040gi--2015.pdf 1040A
https://www.irs.gov/pub/irs-prior/f1040a--2015.pdf Instructions
https://www.irs.gov/pub/irs-prior/i1040a--2015.pdf 1040EZ
https://www.irs.gov/pub/irs-prior/f1040ez--2015.pdf Instructions
https://www.irs.gov/pub/irs-prior/i1040ez--2015.pdf 2015 Tax Tables
https://www.irs.gov/pub/irs-prior/i1040tt--2015.pdf Publication 17 Tax Guide for 2015
https://www.irs.gov/pub/irs-prior/p17--2015.pdf
