No OS installed, don't know what region of firmware to download

So I tried to root my Samsung Galaxy S6 today using TWRP and it got stuck in a boot loop. I went to wipe to cache and accidentally wiped to system. So now there is no OS installed. I know I need to somehow put an OS on the device but I'm in Canada and when I go to samsung's site to download the firmware, there is no Canada option. I bought the phone off of amazon and it came with a European wall charger because it was imported, but how do I know what firmware to download?
Also, when I have found the right firmware, how do I flash it onto the device? I can no longer access TWRP, all I can get is the downloading screen thing. Can I use Odin/how do I use Odin?
Somebody help me I'm panicking because I broke my brand new phone!