As with the case of the iOS 12 public beta, those who wish to take part in the Mojave beta will need to sign up to be part of the beta program on Apple’s website. It is a relatively straightforward process and you’ll be able to start using the beta right away, although it has been recommended that you might not want to use it as a daily driver or on your primary device.
This is because due to the fact that it is a beta, it means that there might be features that aren’t working correctly. There might also be some incompatibility with apps due to drivers that have yet to be updated. However if you are simply curious as to what macOS Mojave will be bringing to the table or if you want to help Apple spot and squash some bugs, then it could be worth checking out.
macOS Mojave was announced at WWDC 2018 earlier this month and is expected to be made available later this year.