I think you should start with the documentation here: http://docs.apigee.com/developer-services/content/add-and-edit-content
This will get you started working with the developer portal.
Dear @VENKATA LAKSHMI KONDAPALLI ,
Apigee Developer Portal is built on top of Drupal 7.0 . Apigee Developer Portal is a distribution of core drupal. If you would like to learn more about Drupal, Drupal.org is the great place to start.
If you would like to learn more about Apigee Developer Portal, like said by @Carlos Eberhardt please refer Apigee Docs portal docs.apigee.com