Change Padding from both side of twenty eleven theme

Try using Firefox with the Firebug add-on for this kind of child-theme CSS work.
https://getfirebug.com/

Look at these:

#branding hgroup {
   margin: 0 7.6%;
}

#access div {
   margin: 0 7.6%;
}

.left-sidebar #secondary {
   margin-left: 7.6%;
}

.left-sidebar #content {
   margin: 0 7.6% 0 34%;
   width: 58.4%;
}

Thanks a lot. It worked fine. But how to change the margine between left sidebar and main body content. In my site it looks many space between left site bar and in main content page. How can I reduce it?

It’s the width in the last CSS section above.

I have added the last code also but there is no change. Would you kindly check again? I wanted to change the main body content left margin. Not Side bar margin.

You need to change the width and the left margin in this:

.left-sidebar #content {
   margin: 0 7.6% 0 34%;
   width: 58.4%;
}

And as has been suggested many times, you really need to learn how to use Firebug so you can sort these out…