Here's how the phrase is typically used:
* "I'm so geeked up for the game tonight! I can't wait to see my team win!"
* "The kids were geeked up for the school dance. They were all dressed up and ready to party."
* "I'm geeked up about the new season of my favorite show. I've been waiting all year!"
"Geeked up" is an informal expression, so it's best used in casual conversation or with friends.