The app is available at the Atlassian Marketplace. To install the app, log into your Confluence as a system administrator and navigate to the "Find New Apps" tab of the Universal Plugin Manager (UPM) in the global administration.
There you simply search for "Accessibility for Confluence". You can find the UPM via the menu entry "Find New Apps" or similar.
If you decide to download the app in the Atlassian Marketplace and install via file upload, make sure that the app distribution file that you want to upload is accessible to your computer either at a file system location or at a network location by URL.
Upload an App
From the application's administration console, click the Manage apps link.
Click the Upload app link at the top right side of the page.
The following dialog appears.
Image 1: Upload app dialog when uploading (click to enlarge)
4. Enter the location of the JAR or OBR file to upload using the file chooser or by specifying a network location by entering a URL. 5. Click Upload. A confirmation message appears when the app is successfully installed. 6. If prompted, restart your application to have your change take effect.
You can now manage the app from the user-installed app list on the Manage add-ons page.
Check your Installation
If the app is successfully installed, you should see the following entry on the page:
Image 2: Entry of Accessibility for Confluence in the Manage Apps tab (click to enlarge)