Can I use turbo tax to amend a 2014 return even if I didn't use turbo tax for that return?

[Critter]

Yes you can but it is not quick, easy or cheap.  It would be better to use the same system that completed the return originally. 

But if you want to ....      

You would first have to fill out a new return in Turbo Tax (and pay for it)  like you were doing it for the first time and hopefully come out with the same results as your original filed return. Then when it exactly matches what you filed and amounts are the same for every line on the 1040 tell Turbo Tax you want to file by mail and print out the original return so TT thinks it was filed, then you can do the amended return.  

See this FAQ on how to amend a return done by hand or by another company
https://ttlc.intuit.com/questions/2939017-can-i-use-turbotax-to-amend-my-return-if-i-prepared-my-tax...