[Sanjip Shah]

@yflyjump To change the background color of the body, in the dashboard, go to Appearance->Theme Options->Design Options Tab->Color Options. Set the ‘Body Background Color’ there and click on ‘Save all Changes’.
For the border of the whole body you will have to use the custom CSS options.
Go to Custom CSS option, paste the following css and click on ‘Save all Changes’.

.wrapper {
    border: 2px solid #000000;
}

You can change the 2px to any number you like, this represents the thickness of the border.
#00000 is the color code, you can changes this to the color code of your choice, you can find the color code in this link http://www.colorpicker.com/. Hope this helps.