If you have a Galaxy S10 series device, the Galaxy S10e, S10, and S10+. You can register for the One UI 2.0 beta program via the Samsung Members app then click on One UI registration notice in the Notices section of the app.
The software version of this update is G970FXXU3ZSJF, G973FXXU3ZSJF, and G975FXXU3ZSJF for the Galaxy S10e, S10, and S10+ respectively. The size of this update is around 2000MB.
If you want to check for the update manually, you can do this by heading into the Settings > Software update > Download and install.