How do I call a template?
 

I wanna add HTML I made to a template in Vbulletin 3.0.0
How would I go about calling that template, having it view on my vbulletin webpage under the header & navbar and before the footer.

Example:

Mysite header
Navbar

(stuff from template)

footer

Thank you

You can try adding this to your phpinclude_start template:
Make a template called 'yourtemplate', enter your content there, then use $yourstuff anywhere you want:)

But how to I call the template? Do I need a .php file to do this? And if so how?

That code will allow you to call a template without any file modification, if there was a file modification - the code would be the same anyway.