There are currently two supported ways that Gamemode 4 modules can be added to an existing Minecraft world: 1-click or for some modules, structure files (1.10+).
If you get problems with installing a module, then post a message here so we can help you further.
1-Click Installation Edit
This method is the easiest for installing a Gamemode 4 module into an existing world, as you don't need any extra software to install it, and as long as you are opped, you can add modules to a server without even having to take the server down first! However, for the 1.8 modules the 1-click will always install the module at bedrock level and will delete any blocks at its location, including other modules so it should be used with care. Current 1.9+ modules are installed at the height of the command block with the 1-Click code.
To install a module using 1-Click, find the 1-click code on the Gamemode 4 website for the module you wish to install, copy it, paste it into a command block and power the command block. It is important that there is plenty of air above the command block in a 3 wide, three long pillar. For a full, detailed explanation describing the correct usage of 1-Click, watch the video below:If you want to turn a Homemade module in a 1-click look here.
Structure File Installation Edit
For some 1.10+ modules, a structure file is available for download. This will allow you to install the module using structure blocks . The downloaded structure file must be placed in the folder: .minecraft\saves\(WorldName)\structures. If there is no "structures" folder, create one with that name. Open the Minecraft world, and place a structure block, set it to LOAD [L] mode, and type in the name of the file. Set the relative position to 0 0 0, if you want the module to spawn where the structure block is (the first command block will be placed 1 block forward in the +x direction). Make sure to set "Include Entities" to ON, then click LOAD. A bounding box will appear, showing where the module will spawn. Right click the structure block again and click LOAD again.
Depreciated Methods Edit
NOTE: THESE METHODS OF INSTILLATION ARE FOR OLDER MODULES AND ARE NOT SUPPORTED FOR NEWER VERSIONS OF MINECRAFT. IT IS SUGGESTED THAT YOU USE THE ONE CLICK METHOD TO INSTALL MODULES.
MCEdit Schematic Installation Edit
Most Gamemode 4 modules have a schematic download that will allow you to import the module using MCEdit. Modules imported using this method may need to have their clocks manually restarted. It is recommended that you avoid importing the module so that it crosses a chunk boundary. You will need to install MCEdit on your computer to install a schematic file into your world. Using this method can have small changes, for instance, Lightning Rods have orange countdowns instead of white ones when imported via MCEdit.
World Download Edit
For some of the older Gamemode 4 modules, a world with the module pre-installed can be downloaded. This is no longer made due to lack of people using it, and the amount of time taken to make one, and some of the current world downloads may have modules that are not updated. If you wish to have a world download anyway, please request one on the forums and it will be considered.