With that configuration you can't (at least easily). I suggest for testing, you add this option:
GeoIPScanProxyHeaders On
From the documentation (http://dev.maxmind.com/geoip/legacy/mod_geoip2/#Proxy-Related_Directives)
When this is set, the module will look at several other sources for the IP address, in this order:
The HTTP_CLIENT_IP environment variable (set by Apache).
The HTTP_X_FORWARDED_FOR environment variable (set by Apache).
The X-Forwarded-For for header (set by a proxy).
The HTTP_REMOTE_ADDR environment variable (set by Apache).
Set that option for testing and remove it when done. Then you can send arbitrary IP's as HTTP headers with curl, ex:
curl --header "X-Forwarded-For: 1.2.3.4" "http://your.site/path"