about 7 years ago - Suggestive - Direct link
From the pinned thread:

ACCESSING THE PUBLIC TEST BUILD
Note: This will download an update over the normal build. There is no way to have both builds available at the same time unfortunately.

Right-Click the Dead by Daylight Application in your Steam Library
Access Properties
Access the "Beta" Tab
Enter the password "DbdPublicTest" (without quotes) in the Text Field
Click Check Code
Select "public-beta" from the dropdown
Restart Steam (not required, but this updates the UI properly and kicks off the download)

DISABLE ACCESS TO THE PUBLIC TEST BUILD
Right-Click the Dead by Daylight Application in your Steam Library
Access Properties
Access the "Beta" Tab
Select "NONE - Opt out of all beta programs" from the dropdown
Restart Steam (not required, but this updates the UI properly and kicks off the download)