How to

Install the addon
Open Blender > Edit > Preferences > Addons tab (left panel), then click Install (top right) and locate the zip file of the addon

Use desktop notifications
In the addon preferences, toggle Desktop notifications

Use Discord notifications
In the addon preferences, toggle Discord notifications.
Enter your Discord ID. This can be found on Discord: enable Developer Mode (Settings > Advanced), then right-click on your avatar picture in a conversation > Copy ID
Enter your Webhook URL. This URL can be found on your Discord server (or server you are an admin of) under Server Settings (gear icon) > Integrations > Choose or create a webhook.

Use Pushbullet notifications
In the addon preferences, toggle Pushbullet notifications.
Enter your Pushbullet token. It can be found on the Pushbullet desktop website under Settings > Account > Access Tokens