You must have a fork of the main rusefi repo as well as a fork of the rusefi_documentation repo. Clone your fork of the rusefi_documentation repo:
git clone [email protected]:<your username>/rusefi_documentation.git
From your clone, add your wiki as a remote and push to it.

git remote add wiki [email protected]:<your username>/rusefi.wiki.git
git fetch wiki
git push wiki

This will get your wiki2 up and running. Now you can make changes, and run

git commit -am "your commit message"
git push wiki

to test them on wiki2.
You might have to use git push --force wiki.
Also, note that the changes must be in the master branch of your fork for this to work.

If you want the changes to be synced automatically, you will have to change rusefi/rusefi.wiki.git to /rusefi.wiki.git in your fork's action files.
Specifically, these action workflows:
rusefi_documentation/.github/workflows/sync-wiki2.yaml
rusefi_documentation/.github/workflows/sync-wiki3.yaml
rusefi/.github/workflows/sync-wiki.yaml
You need to set up an access token in your repository secrets for Actions.

The easiest way to test Wiki3 is locally. You could also set up a webserver and your repository secrets to let the workflow upload it for you, but here I'll just explain how to test locally.

There is a script included in the repo that will install all necessary software if you are running a Debian/apt-based Linux distro.

bash ./wiki-tools/install.sh

If you aren't using a compatible OS, read the script to find which packages you need to install.

Once the necessary software is installed, you can now generate the site.
There is a script included to do this as well.
Run bash ./wiki-tools/run.sh, and the site files will then be found at ./generator/wiki