- Purchase Fallout 4: GOTY from GOG.com. Purchase (add) Fallout London from GOG.com. You now have both of these in your GOG library.
- Download and install GOG Galaxy. It just makes this whole thing easier.
- In GOG Galaxy, install Fallout 4: GOTY. Once completed, run it (at least) once to the title screen.
- In GOG Galaxy, install Fallout London (which just installs the mod installer). Once completed, run it and use the installer to install the mod to the Fallout 4: GOTY folder (typically
C:\Program Files (x86)\GOG Galaxy\Games\Fallout 4 GOTY
). - Download "High FPS Physics Fix" from Nexus Mods. Download the one specified for Fallout London.
- Extract the files. Make sure the following files are located at:
C:\Program Files (x86)\GOG Galaxy\Games\Fallout 4 GOTY\Data\F4SE\plugins\HighFPSPhysicsFix.dll