In one sentence, describe what the following article is about:

It's the blue app with a white "A" on it. This is where you download and install new apps. It's located in the lower-right corner next to the icon of an hourglass. Tap the gray search bar at the top and type plex on the on-screen keyboard that pops up. Then tap the search key to perform a search. The Plex app has a black icon with a yellow chevron pointing towards the right. When prompted, use your Touch ID or device passcode to download and install the Plex app. If you don't have any security on your phone, tap "Install" to start the installation. This will appear once the app is installed. This will launch the Plex app. If you already have a Plex account, choose whichever method you used to create your Plex account when you installed the media server on your computer. If this is the first time using Plex on your iPhone or iPad, you can tap "Next" to view the introduction or you can tap "Skip Intro" to go the main page. It's located in the upper-left corner and has the name of your iPhone or iPad. If you want to view videos on your computer, tap your computer's name or the name you gave to the Plex Server you set up on your computer. It's the second tab at the bottom. You can choose Movies, Music, Photos, Channels, or Playlists. This will allow you to browse all the files and folders in your media library. This media will start streaming to your iPhone or iPad.

Summary:
Open the App Store . Tap the Search tab. Type plex into search. Tap GET next to Plex. Enter your Touch ID or passcode. Tap OPEN. Tap a sign in method and log in. Tap your device menu in the top-left. Tap the device you want to stream from. Tap Browse. Tap a category. Tap Browse again. Tap the media you want to stream.