How to flash TWRP & deal with dm-verity

Ok ok, to start this off... I'm a Mac user. hahahahahahahahahhaahahahahaha But my gramps recently moved in and he has a Windows laptop. He lets me use it whenever I want, and gee, it even helped me recover my phone bc it got in a boot loop bc I was using a very early version of sungstraum. Ok so what do I understand here:

-Must have OEM Unlock option ON

-Flashing TWRP and swiping to allow modifications will trigger dm-verity which won't let my phone boot

-Don't use a Mac for flashing devices

But what I don't get is:

-Get through dm-verity

-I have no idea if flashing a custom kernel will get rid of dm-verity

And I need your help! dodododo dora I just need simple instructions to get around dm-verity and happily flash a custom kernel and Magisk. I'm running Android Nougat and I have a G920T (Not a G920T1 a.k.a TMobile S6) (Yes my phone is unlocked). If I need to paste in more info, I will do it.

All to modify my device!!!

Kthx Reddit.