How to enable sudo
i want to know the steps
You don't enable it.
It is enabled. You just use it.
Look at http://ubuntuguide.org/wiki/Ubuntu:Jaunty
If you are new to this, as your post indicates, first a warning SUDO lets you into commands that could damage your setup. Use with care!
Think of it as Supervisor User wants to DO something...
Then at the prompt which will probably be a $ or a # in a terminal screen simply type SUDO and the command that needs to be done like this
prompt$ SUDO gedit
when return is typed it will ask for a password for the user name shown.
A quick help is SUDO!! which will repeat the last command so that it doesn't have to be retyped everytime.
Hope this helps.