Pull requests are welcome from the Community. This Guide is for you after all.
The general edition of the Guidebook is managed by @w3c/guidebook but many areas are maintained by separate individuals or teams (check out the commits history of a file to see who).
Avoid editing the files within a submodule, unless you want to struggle updating the submodules later. Edit those in the dedicated repositories instead.
The exact commit (e.g. revision) of each submodule is stored in the w3c/guide repository. Those needs to be updated in order to expose the latest version.
If it's the first time you check-out the repo you need to use --init first:
git submodule update --init --recursive
After that, you can update to latest tips of remote branches:
git submodule update --recursive --remote
then commit your updates
git commit -a -m "[chore] submodules update"