File versioning happens automatically by default. It technically uses the Versions app but that is built in and maintained by the core Nextcloud team, so you can think of it as a built in feature (but can be disabled if you want). The Admin guide you referenced talks about the default settings and how to adjust them, but perhaps what you’re asking for is provided in the User guide which talks more about how to view and restore file versions as an end user (https://docs.nextcloud.com/server/stable/user_manual/files/version_control.html).
File versions are automatically created every time a changed file is synced (you save a file, the client syncs it, then you make changes to that file and it gets synced again, etc.).
As far as I know, you can only access previous file versions from the browser. There is no way through the official client on Windows, Android, or Linux that I know of. I can’t say for sure, but that would indicate that they may not have support (yet) for file versions through the API.
How to: Basically sync files, and whenever the need arises to go back to a previously saved version of that file, log into your account through the browser, open the details for that file, and restore a previous version.