You'll get the Discord Integration settings in Settings > Plugins > Discord Notification > Discord integration.

You need a webhook url to integrate. Please follow the steps below to get that:

Go to your server/workspace of Discord and go to server settings. 

Go to Integrations tab and then Webhooks.

Create a New Webhook.

Customize the information.

Copy the webhook url and save to the integration setting. 

After saving the credentials you'll get a button to test the notification. Click on that to check if it's working properly.

Now go to Discord notification settings tab and enable notifications for your desired events.

Please note that there must be web notification enabled in app notification settings (App settings > Notifications) for those events to get Discord notification.