Then address the following prayer to Lord Markandeya:
मार्कण्डेय महाभाग,सप्तकल्पा जीवितह
चिरन्जीवी यथा त्वं,लाथा मे भ्रातारं कुरुः
Markandeya Mahabhaga,Saptakalpa Jeevitaha
Chiranjivi Yathaa tvam tathaa me Bhraataaram Kuruhu.
Meaning: O Lord Markandeya, You are most fortunate and are Chiranjeevi (immortal), who will live for the duration of seven Kalpa, Please grant my brother a life as long as yours by virtue of being a Chiranjeevi.
Not a regular common practice for daily prayers but it is followed for special occasions. For taking the kind of shankha it is beneficial to have a shankha that is “dakshin Varti” which means circling towards the south(opening) is best. Any size you can find is fine.
Now take the sankha and dip it in the water of the kalash and take the water into the shankha. take a couple leaves of tulsi if you have , if not then some plain rice or few petals of flower are also fine. Now take this shankha and place it in a copper plate that is called Tarbhaanu.
a stainless steel plate is also ok.
Join your hands in prayer and say the following shloka to bring the shankha as part of the ceremony. Shankha is considered to have born from the ocean so invite Lord Vishnu and Shankha to the special occasion.
video and the written format of the shloka is as below