From Fedora Project Wiki
Provision Fedora CoreOS and configure fedora-toolbox:35 .
- Download and verify the latest FCOS next image (pick the right image for your environment).
- Toolbox is preinstalled on FCOS 
Note: Use the latest image registry.fedoraproject.org/fedora-toolbox:35
How to test
- Create an Ignition file.
- Launch your Fedora CoreOS system using this Ignition file. See the Quickstart and the provisioning docs for a guide how to launch FCOS in most environments (bare metal, virtual, cloud, etc).
- Follow the documentation for Debugging with Toolbox and execute some debugging commands.
- You can SSH successfully into your FCOS system.
- Once inside the toolbox, you can access common command line tools, and install new ones using a package manager (e.g., DNF on Fedora).
- Once done with your container, you can exit the container and then remove it from the host.
- The linked documentation makes sense, nothing is obviously missing, and the instructions are clear.