[Reeve of shinra]

Your going to be doing a lot of poking around to get the basics down.

admincp - styles and templates - edit style
Edit your style and at the bottom is an option to add a template.
The template is added to that style and its children ONLY.

for example:

Parent Style One (I added a new template "x" here)
- Blue Style
- Red Style
- Green Style
(these inherit the properties of Parent Style One, including the new Template but we can change each style as needed, in this case to have a different color)

Parent Style Two
- Gray
- Orange
- Purple
(These styles didn't get template X because they don't roll up to Parent Style One)

The templates are stored in the database and the php files call them through an eval.

Here is a good tutorial for creating your own vb powered php page (ala hello world) which goes through the basics of creating a page that fully taps into the power of the vbulletin backend.... meaning you get to use your forums header, footer, templates, phrases, user info, etc.

[How-To] vBulletin API Basics: Creating Custom Pages & Misc.

That is further expanded on here with many variables you will want to use.
[How-To] vBulletin API Basics: Variables, Functions, Objects

Here are some others I bookmarked:
Adding the vbulletin editor into your mods
Using the vbulletin database class

There are more here:
https://vborg.vbsupport.ru/forumdisplay.php?f=218