How to configure Apache

I’m trying to use apache instead of nginx, but I failed to configure apahce (in ubuntu), the problem is what should I write in argument “DocumentRoot”. I’ve see the configure file in

needed for downloading attachments

DocumentRoot /home/git/gitlab/public
I’m confused by it cause I don’t know what should I filled behind of “DocumentRoot”.
I installed gitlab in few months before, I removed it and delete files in /home/git after I failed to configure it. I’m a newcomer at this so I’m very want to know how can I do to slove that, thank you.