I have docusign account, but I do not see any option to create sandbox account when logedin in docusign account. How to create that one?
Sandbox accounts are freely available from the DocuSign Developer Center. Note that the Demo environment is entirely separate from Production - the accounts won't be directly related, although you can register for a Demo account using the same email address as your Prod account if you link.
Direct link to the sandbox signup page: https://secure.docusign.com/signup/developer