I have installed the app in our Splunk Cloud environment. I can now add Slack to new alerts I create. However, when the alert is triggered, the Slack post doesn't come through (I can receive emails). I never added a webhook for Splunk to connect to Slack. Is there a help page on how to do that?
Here's what I've found on Slack's site for creating web hooks. I've not done it myself, but maybe this URL will help you out...