Finding the center - Setting an offset in the Start-Gcode

Introduction
I've upgraded my Anet A8 stock hotend to the E3D v6. The mounting for the hotend is slightly different, so that the printer isn't correctly centered to the bed. When printing small things their isn't any problem, but when I wanted to print things that nearly take the hole buildplate it can be tricky to align the things so that they are printed fully on the platform not midair.
These instructions should help you edit your Start-Gcode to counteract this problem.
I have an Anet A8, this tutorial will most likely also work for your printer, if it runs Marlin Firmware. For slicer I am using Cura 3.1.0, in different Versions or slicers this process may be different.
My solution works good, but you should change the offset in Firmware. Than the printer has the offset stored in his memory so that the printer knows this offset not only your currently printing part. There is an Tutorial for this https://www.thingiverse.com/thing:2280529 by thingiverse user 0scar.

Instruction