Connecting Mailgun integration is very simple. Following the image shown above, simply click on the Connect button and follow the prompts from the resulting Mailgun window to add up your Mailgun Keys.

If you ever need to disconnect your MailGun integration, you can click on the Disconnect button as shown in the image above, on the MailGun integration window.
Follow the disconnection prompt and you're done.
Note: after disconnecting your integration, Belugar will automatically invalidate and delete any record it holds for your integration and will not be in possession of it thereafter.
If you ever need the integration, simply follow the Setup Guide again.