jQuery implemntation

I really need help linking my theme to jQuery so that I can include it in the header, page, or footer.
This is what I’ve done thus far:
I concluded that I want to link my theme to Google jQuery API access.
I have read several different methods which include linking to the jQuery in the theme’s functions.php file, in the header.php file.
Some tutorials use the “wp-enque” script, but I have had no luck.

I learned jQuery on CodeAcademy and am really excited to implement it on my sites, but this is really hindering me.
Thanks for the help!