After the app is installed, you'll be able to see Plex in the list of apps.
It is possible to activate Plex on your TV
After installing and downloading Plex Media App, after downloading and installing Plex Media App The next step is to connect Plex to the TV. To do this, just:
Launch the already installed Plex app.
Don't overlook how to fix Plex TV inoperable with Samsung Smart TV, Roku, LG, and some other smart TVs on Tizen along with WebOS.