How to use functions in template

[ZomgStuff]

How do i use a function like this

function fetch_userinfo(&$userid, $option = 0, $languageid = 0)

in my own template, one that I'm making following this guide
https://vborg.vbsupport.ru/showthrea...+your+own+page

Well an easier question, how do I get it to run and not show up as text?

The page just displays this

fetch_time_data();