Hi Himanshu,
Please follow the below steps:
Setup > Enter Escalation Rules in the Quick Find box > Select Escalation Rules
Then choose new, and give the rule a name. Specify whether you want this to be the active escalation rule. Click Save.
To create the rule entries, click New. For each entry, you can specify the following:
Order, Criteria, Specify business hours criteria, Specify how escalation times are set. Then click Save.
Click New to add an escalation action. You can specify the following:
Age Over, Assign To, Notification Template, Notify this user, Notify Case Owner, Notification Template, Additional Emails.
Thanks