Once you're in the notifications menu, you can see the Hipchat configuration settings.
Hipchat works by configuring webhooks that receive data, that in turn will be posted to a room in your HipChat. HipChat's official documentation explains in detail how to create your webhook.
Here's how that might look:
[fqdn] is your fully qualified Hipchat domain name (for example,
[id] can be a numeric room ID or its display name.
On the Oh Dear! side, you only need to copy/paste your HipChat webhook in our notification setting, determine which events should be sent and you're done.
The room that receives your message will be part of the webhook URL. To change the room your messages get sent to, change the webhook URL to match the correct room ID.
For more details, see the official HipChat documentation on webhooks.