Can I get my taxes back from the last 4 years now that I left USA and got back to my home country? What do I need to do?

[xmasbaby0]

The last four years?   No.  It is too late to receive an income tax refund for any tax year earlier than 2017.  A refund for any earlier year has now been forfeited.

You say you went back to your home country--so we do not know if you can even use TurboTax or if you should use an alternate software.  That depends on whether you are a non-resident alien.  

NON RESIDENT ALIEN 

If you are a non-resident alien, your return must be filed on Form 1040NR, which cannot be prepared using TurboTax.  You can use TT’s partner, sprintax:

https://www.sprintax.com/non-resident-alien-tax-1040nr-turbotax.html

[Opus 17]

If you are a resident alien (you are not a US citizen and not a green card holder, but you live and work in the US) you owe US income taxes on the money you earn while you are living in the US.  There is no law or treaty that I know of that says you can get a refund once you return to your home country.  Why do you think that?