TYPO3 Core

Hi

I'm trying to use typo3 cli with no success.

Using command:

php ./cli_dispatch.phpsh extbase help

I'm still getting error:

Oops, an error occurred: TYPO3 Fatal Error: No database selected!

I was looking for some documntation for cli but with no success.
Can you give me some hints how to use cli, or where is the problem?

Thank you