How do I

i know this has been answered im a newbie i dont get it.

how do we add a timer thought out your game

You can use a custom plugin, the Time Manager plugin.

Not is my intention doing any type of minimodding, but please, insert a title before "How do I". Your post need a title. "How do I" is only an default to start before your title.

Can you just create a global object - a sprite which does nothing - and attach a timer to it ?

Yes! Just use the "Timer" behavior.