You are completely free to copy someone else's code. (providing credit for that code is appreciated)
Using Page Layouts
The easiest way to use the new page layouts is to copy the code into a text editor program and edit it there. With the game open in one window and the wiki page layout open in a window next to it, it is easy to flip from one to the other. I prefer to use Notepad.
I like to be able to test my templates and major page changes before I save them on the wiki. To do this, I have installed a web server on my personal computer and then installed my own wiki. Expect to make mistakes unless you are experienced doing this. I do not recommend this unless you plan to make lots and lots of contributions.