A few more steps...
Back up your Mac
Please note that you are about to install beta software. Always back up your data and files before installing beta versions of macOS. If you have multiple Mac computers, we strongly recommend installing on a secondary system. Backing up files on a Mac is easy with Time Machine, the built-in backup utility.
Enroll your Mac
When you enroll your Mac using the macOS Developer Beta Access Utility, you get access to developer beta software. Just go to BetaProfiles.com to download the utility and run the installer. Please follow the onscreen instructions.
Download the macOS developer beta
After you’ve completed enrollment, you will be prompted to download and install the macOS developer beta from Software Update in System Preferences. Click Upgrade Now to get the release. If a developer beta is not available, you will receive a notification when it is released.
Install the macOS developer beta
After the macOS developer beta has finished downloading, the installer launches and guides you through the installation process.
Stay on the latest macOS developer beta
When a new developer beta is available, you’ll receive a notification from Software Update. You can install the developer beta from Software Update in System Preferences.
You can always delete this installed profile anytime you want to stop receiving developer beta updates. All you need to do is go through the Delete Profile page, which has all the instructions for each of your devices.
However, if you want to roll back to the previous stable version, you will probably need a macOS installer for the version you want to roll back to. There's also a Restore guide if you're interested.