Point your browser to https://api.slack.com/apps and choose Create an App.
Enter "CloudRadar" as the name of the new app. Then select the Workspace you want to use.
After clicking on "Create app" you are asked a few questions. Choose Bots, and then choose Add a Bot User.
Give the bot user a name like
On the top right choose Your apps. Cloudradar appears in the list - choose it, and then choose Install App to your workspace.
You need to confirm this step with the Auhorize button:
On the left, choose Install App and copy the data from the Bot User OAuth Access Token field.
In CloudRadar, start adding the recipient that should receive notifications via Slack, and paste the data you copied in the Bot User OAuth Access Token field.