I did a search on the forum already and also went on bmwe34.net

but im still confused "hence a newb", bare w/ me ladies and gents..

I have a 1990 e34 525i
I havent driven it for about 3 years and the battery is dead i tried opening it w/ the double locking system but no deal, i read about people using a battery charger of some sort but i confused what it is? is it a regular jump start or batter charger pack? if possible anyone can give me a picture of the battery charger specifically what i can use to give power to the trunk light and remember im a newb give me a warning where to plug it in? and where i can purchase one?

thanks sorry if this may be confusing..