How do I get a copy of a federal tax return that is more than 7 years old (2012)?

if you didn't keep a copy then you are out of luck. Neither Turbotax nor the IRS maintain tax returns going back that far.  However, the Social Security Adm would have copies of any W-2's (not a complete 1040) you received for that year. But there is a fee.

https://faq.ssa.gov/en-us/Topic/article/KA-02501 

Sorry.   TurboTax and the IRS keep tax returns for seven years.   If you did not save a copy for yourself then you are--as stated above--out of luck.   Going forward---save your own records and make copies of your tax returns.