An important thing to note, the less players there are in your game, the less time it takes to power a generator.
There are 6 generators to turn on. You can only do one generator at a time.
To turn on a generator, you must activate the panel on its center structure. The price is 200 points (+200 more for every extra person in your game). Doing so will start to fill a meter. This will also spawn in medieval knight looking zombies. You must stay on the generator platform until the meter is filled. Stepping off the platform will cause the meter to drain, and will shut off if left unattended for too long.
In co-op, having more players on the generator platform will fill it faster. You can kill the medieval knight zombies, though they will spawn again.
Once a generator is powered, the knight zombies will die and you will be refunded your money.
On a random round, a generator will get attacked by the knight zombies and the power meter will start to drain. You must kill them before they shut off your generator. If it turns off, you'll have to restart it.
If you want to play the safe route, activate all generators in a single round.
1st generator - In the spawn.
2nd generator - Buy the spawn door by the first generator and follow the trenches and through another door. It will be in front of you.
3rd generator - Buy the other spawn door and follow the trenches and through another door. The generator will be up the steps to your left.
4th generator- From the Workshop, head out to No Man's Land. Follow the trenches to the left of the Excavation Site.
5th generator - From the Workshop, head out to No Man's Land. Follow the trenches to the right of the Excavation Site and buy the stone debris.
6th generator - On the opposite side of the Excavation Site is a burnt down Church. Follow the path through the Graveyard into the Church. Clear another piece of debris by the stairs beside the Tank. Head up and outside into the trenches to the last generator.