You can download the plugin from the Atlassian store.
To upload the add-on:
1.     From the application's administration console, click the Manage add-ons link.
2.     Click the Upload add-on link at the top right side of the page.
The following dialog appears.
3.     Enter the location of the JAR file to upload using the file chooser or by specifying a network location by entering a URL.
4.     Click Upload.
A confirmation message appears when the add-on is successfully installed.
5.     If prompted, restart your application to have your change take effect.