Hey there Padmavathi,
I am real sorry about the late response on this, thank you for being patient! Were you able to figure out how to install applications? If not, I'd be happy to help out! The steps I'm going to provide are taken from this article.
"Search for an app
Browse for apps
Tip: If you have trouble with your purchase, try a different payment method, like a credit card or PayPal. Learn how to add a payment method."
I hope that helps! If you have any other questions or concerns, please let me know.