...
In your Graylog account, go to Alerts from the main menu.
On the New Notifications page, select Notifications.
Enter a Title and a Description for the channels you want to set notifications for.
Select HTTP notification as a for the type.
Paste your integration URL (copied while adding the integration in Jira Service Management) into the URL field.
Select Create and save the changes.
Select Event Definition.
Enter values for Event Details, Condition, and Fields to create the notification rules.
In Notifications, select the notification you created earlier.
...