Can some one explain to me how this works? Obviously I just have to maintain a larger output than my population? but how much more? It was so much easier in CIV4!

I agree. At the very start of the game I started building Stonehenge and when it finished my borders shot out. It was at least 6 squares out in every direction, no lie. I didn't even have any temples built.

Can some one explain to me how this works? Obviously I just have to maintain a larger output than my population? but how much more? It was so much easier in CIV4!
The Great People generation rate appears to be linked to the culture level of your civilization, so it helps to have a high level.

The Great People generation rate appears to be linked to the culture level of your civilization, so it helps to have a high level.

They pop everytime you hit a great person milestone. Hold your right trigger, you'll see it. It's like a level up bar.