MrBean35000vr (creator of CTGP-R, a Mario Kart Wii content pack) created a Wiimmfi Disc Patcher that allows you to insert a disc and patch the game on-the-fly for Wiimmfi use, though this must be run every time you start the disc.
You may not want to run a patcher each time you want to play on Wiimmfi, and maybe you already use a USB Loader. As such, ISO Patchers were created, some for specific games.
* Wiimm's Disc Patcher: You need [this](http://download.wiimm.de/wiimmfi/patcher/mkw-wiimmfi-patcher-v6.zip) one if you're patching Mario Kart Wii, [this](https://github.com/RiiConnect24/ACW-Patcher/releases) one if you are patching Animal Crossing Wii, or [this](http://download.wiimm.de/wiimmfi/patcher/wiimmfi-patcher-v4.7z) one for other Wii games such as Super Smash Bros: Brawl.
1. Run the patch script for your OS: usually it will end in `.bat` for Windows and `.sh` for Mac/Linux.
1. Once it's finished, get the version out of the `wiimmfi-images` folder (it may be in the folder before the patcher - ../wiimmfi-images) and copy it back to your USB.
* Mario Kart Wii Competition Patcher [Wii](https://competitions.wiimmfi.de/competition-tool-wii.zip) / [Wii U (vWii)](https://competitions.wiimmfi.de/competition-tool-wiiu.zip)
1. Extract Mario Kart Wii Competition Patcher and put it in the `apps` folder on your SD Card.
1. Insert your SD Card into the Wii.
1. Launch the original Mario Kart Wii game (not Wiimmfi patched).
1. Navigate to Settings -> Network Settings (or Nintendo WFC Connection) -> Message Service. If you turned the message service feature on, turn it off and turn it on again.
1. Launch Mario Kart Wii Competition Patcher.
1. The patcher will look for save files for Mario Kart Wii on your storage device in various places, and upload them. This is done in case a missing competition is found in your save file. It will also, of course, patch your Wii for competitions.
If you're using the Wii U, you will have to run the competitions patcher whenever you want to check for a competition, because WiiConnect24 is not enabled on the Wii U.
MrBean35000vr and Chadderz have an amazing CTGP-R distribution, the application that allows you to use a set of custom tracks, has automatic Wiimmfi patching. Go to the [ChadSoft Website](http://chadsoft.co.uk) for the download and instructions.
Huili has put together a really good collection of custom tracks and hacks called MKW Hack Pack, and it allows you to connect to Wiimmfi. To learn how to set it up, go to the [wiki page](http://wiki.tockdom.com/wiki/MKW_Hack_Pack).