In this context it means "to watch/guard the place", "to look after the place".
In 1997, he went to work in Dongguan as a "watcher" for a timber factory. There, he learned about the the Han lifestyle, played pool with friends and sang in karaoke bars.
I'm translating a bit freely here, but that's the geist. 给人看场子 means "to watch/guard the place for someone else", but it conveys the idea of informal work.
The subject of the sentence wasn't a formal security guard, or supervisor. He was "helping someone look after the place", "making sure things ran smoothly".
Bonus: Baidu Baike has also a page about this term, meaning essentially "bouncer", or even "henchman" for club and bar owners. However it doesn't look like this page is written very professionally, so it's probably a very colloquial, extended meaning, or possibly underworld lingo. I would take it with a grain of salt.