Beginner help with out of sync local repo

Hello,

I'm learning git/github it's great, however I'm stuck/confused with this issue below and wonder how I fix it.

I've build a new virtual server and to build the rest of the server I scripted it and put all the scripts into github. I git clone the repo and ran the scripts and all is up and running, however the local repo things all is new:

/opt/mybuild$ git status
fatal: detected dubious ownership in repository at '/opt/mybuild'
To add an exception for this directory, call:

git config --global --add safe.directory /opt/build

How can I get this in sync with the github repo again?

Thanks