For installation provided by Snapdeal, the service engineer will call you within 24 hours of delivery of your item. He will book a time slot for installation, per your convenience.
For installation provided directly by the brand, you need to call them to book the installation once your item is delivered. You will find their contact number under the "Installation and Warranty" section of your item's page.
In case you face any issues getting your item installed, please write to us in 'CONTACT CUSTOMER CARE'.