You'll need to set the app up all over again, and there will likely be updates available the next time you check the Play Store. You should immediately see the app reappear in your app drawer, but keep in mind that any data from before disabling it is gone.
Locate and tap the app you wish to enable.Locate the Apps section (the exact name will vary, depending on your phone). The simplest way is to search for the app on the Google Play Store, then tap Enable where you'd typically see an Install button, but if you'd prefer to see a list of your disabled apps, that's easy too. Should you decide you want to give an app you've previously disabled a second chance, there are a couple of ways to re-enable them. Once disabled, you should no longer see the app on your home screen or throughout the system. All it does is provide an empty URL bar for you to enter download links for apks, the files Android devices use to install apps. This app is completely free and can be found on the Amazon appstore in your Fire TV.
That's it! Your phone will immediately delete as much data from the newly disabled app as possible, including any updates it might have received since initially setting up your phone. The simplest way to sideload software onto your Fire TV is to use Downloader.