What data do you want to import? You can't import K-1. If you start with the oldest return then you can transfer it into the next year to start the next year.
Do you have the Desktop programs for each year? They only sell the last 3 years so you can't get 2015 anymore and 2016 will be dropping off soon too.
To do a prior year return you have to buy the Desktop program here, https://turbotax.intuit.com/personal-taxes/past-years-products/2017 You will need a full Windows or Mac to install it on.
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...
