Just unzip the downloaded folder and upload all the content to the respective folders in admin and catalog in your store.
After that go to "Modifications", click "Refresh" and done.

It's very simple and it doesn't change any files in opencart.
It just will add 2 new Free Shipping ways.
You have your original "Free Shipping" that you can use for local sales (your country) and the new ones you can use "Free Shipping Europe" for sales in europe and "Free Shipping World" for the rest of the world. You just need to configure it at your way.

I tried and i have it running in Opencart 2.0.1.1 but i think it will work in all versions.
This is in english, if you want it to other languages you just need to edit the language files and upload them to the respective language folders.