In order to unlock you need to visit "Death's Office" which is a unique area found in all major respawn points (marked with a cross symbol on the map).
The earliest you can get this is just after tutorial island when you spawn in lumbridge. Run south towards the graveyard in the corner to the right once you come through the gate there is an open grave. Interact with this to be teleported to deaths room once you enter your achievement will pop straight away.
Video Guide.
Starts - 00:14