Finding the <body> tag?

[HUMMERh3]

What file or template do I need to use to edit the <body> tag for my vbulletin forum?
I need to add "onLoad="IPOLoad();"
I found a suggestion:

The body tag is in your Admin CP -> Styles -> Modify -> [fonts/colors/etc] -> Body Tag

But in the drop down menu I don't see where to find the body tag. It lists
All style options
common templates
stylevars
main css


Which one do I choose?

[ranz]

If you use the Search In Templates feature and use "<body>" as your search parameter - you will find all the templates with the Body tag.