No you can't add years together.
How to prepare a prior year return
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-prepare-a-prior-year-tax-return/00/25...
How to finish a return you started online
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...
You can't do a prior year return online or efile it, but you can buy either the cd or download the desktop versions for the last 3 years from Turbo Tax here....
http://turbotax.intuit.com/personal-taxes/past-years-products.jsp
Or you can check for Turbo Tax for all years on Ebay or Amazon, etc.
Either way you will have to mail in your return. And if you are doing more than 1 year, send each year in a separate envelope. Sometimes the IRS will just staple all the sheets together and miss a second return.
