how to enable email alert for site errors

hi ,

In 24.2 version we have received a feature as New site email alerts will be sent to site object administrators,

• Is we need to enable manually or it will send automatically to the administrators if it wil fails anything on the site page.
• If it sending automatically then I'm getting any mail from site error alerts.

Note : Currently we are using 25.1 version and I have administrators access for all objects in our application 

could you someone help me how to enable for that.

Thanks