In addition to the answer from @Gaeilgeoir:
The prerequisite on the Box 5 is that you have logged in to the box with a Google account. If not, you cannot use the Google Playstore and therefore no additional apps such as. B. Install Joyn.
If you don’t have a TV box or want to use it directly on the TV, then go to the Google Playstore on your TV, and if it’s not an Android TV operating system such as. B. at LG in the area from the home screen to apps. It always depends on the TV brand. In some cases it was installed automatically after starting the streaming service, or is now available with an update.