An administrator is identified by the --admin parameter when starting wiki. The admin value would depend on how individuals are identified by the security module in use.
To set an admin user you should add the following to your config.json:
"admin": {"google": "1234xxxxxxxxxx"},
As long as you have that line in your config.json file - you should have admin user rights. make sure you are logged in, and that you restart your wiki server after making and changes to config.json.
Make sure your upstart script is nice and plain as well (see example).
Changes will apply to the origin site and all other sites hosted by the same server should that be a wiki farm.
# See also