Is there a straightforward way to uninstall this App?

Getting error messages that 

Apex script unhandled exception by user/organization: 005A0000000c7Up/00DA0000000artp

Failed to invoke future method 'public static void callout(String, String)' on class 'ifttt.Webhook' for job id '7072G00006hfzHN'

caused by: System.CalloutException: Unauthorized endpoint, please check Setup->Security->Remote site settings. endpoint = http://ifttt-salesforce.herokuapp.com/ifttt/v1/webhook/opportunity_was_won

Class.ifttt.Webhook.callout: line 33, column 1

New to organisation as Admin and no-one in organisation aware of App being used