The new macOS High Sierra 10.13.2 beta can be downloaded from the Apple Developer Center or through the Software Update mechanism in the Mac App Store with the proper profile installed.
It's not yet clear what improvements the second major update to macOS High Sierra will bring, but it's likely to include bug fixes and performance improvements for issues that weren't addressed in macOS High Sierra 10.13.1.
No significant new features were discovered in the first three betas of macOS High Sierra 10.13.2, but we'll update this post should notable changes be found in the fourth beta.
The previous update, 10.13.1, introduced fixes for some serious security flaws and brought new emoji to the macOS operating system.
Update: Apple has also made the fourth macOS High Sierra 10.13.2 beta available for public beta testers.