This is How you root your Samsung Galaxy S6 and S6 Edge running on Marshmallow, please check your model number before downloading the respective Recovery files.
Flashing a custom Recovery allows you to flash custom ROMs on your Galaxy S6.
Read further for more info.
RECOVERIES & KERNELS!
Check Your Model number
Download Recovery & Kernel (ending in tar.md5) –Download
Please Follow the Instructions carefully!