Every software comes with a manual or "read me". Stata is not an exception.

Dear Harisankar

Please, visit the following links, I hope will be useful for you.

https://stats.idre.ucla.edu/stata/modules/

http://www.princeton.edu/~otorres/Stata/

http://data.princeton.edu/stata/

Good Luck

Thank you Mr. Etuk and Mr. Hassan for you suggestions.

Please check the following link. I try to put all the online resources in a place

https://statisticianrayhan.blogspot.com/2017/02/stata-online-resource-for-learning.html

Thank you Mr. Islam. The link was helpful.

Dear HK

You may use a book entitled "A Gentle Introduction to Stata", 4th Edition by ALAN C. ACOCK.