There is details on how to disable the automatic checks and updates on the doc site
There is no graphical configuration tool available yet to setup automatic upgrades, so you need to edit files manually and run commands from the terminal to get it setup.
First check what the current configuration is of automatic upgrade by running the rpm-ostree status command in the terminal. The first line of the output will show if automatic upgrade is enabled or not. If it says AutomaticUpdates: disabled then automatic upgrade is not enabled. If it says AutomaticUpdates: fetch then an upgrade will be downloaded but not staged. If it says AutomaticUpdates: stage the upgrade files will be downloaded and copied to the new image that will be activated after a reboot. To enable automatic ostree upgrade, do the following:
Edit the file /etc/rpm-ostreed.conf and in the [daemon] section, uncomment and change the line that says #AutomaticUpdatePolicy=none to AutomaticUpdatePolicy=fetch to download the upgrade files only, or change it to AutomaticUpdatePolicy=stage to download and copy the files to the new OS image. Then save the file.
Run the command rpm-ostree reload to make rpm-ostree aware of the configuration changes.
Start the systemd unit timer by running command sudo systemctl enable rpm-ostreed-automatic.timer and then sudo systemctl start rpm-ostreed-automatic.timer.
The default timer configuration is set to be triggered one hour after boot and then repeat every one day thereafter. To change the timer frequency, edit the file /etc/systemd/system/timers.target.wants/rpm-ostreed-automatic.timer
You can check that the rpm-ostreed-automatic.timer is enabled by running the command systemctl list-timers. If it is in the output list, then it is enabled.
Disable Automatic Upgrade
To disable automatic upgrade, disable the rpm-ostreed-automatic.service with the command sudo systemctl disable rpm-ostreed-automatic.service.