Classic upgrading a legendary

Maybe I am just missing something big here... I can't finger out how to get Cinders. People have been telling me to run higher Torghast, but does that just mean the hardest one? Because I have been struggling a bit with those. I tried running a higher layer on the easier ones but for a layer 6 it says I need a torment and I don't know how to get one and google hasn't been helpful. One person mentioned running a lower to get one, but I just ran a 5 and nothing. via /r/wow https://ift.tt/wRs29Jz