I wish the OpenVPN documentation would be more clear about this business of proxy setting.
That document explains how to connect to an OpenVPN server that is operating behind a proxy server. What you want to do is different: you want to connect to your OpenVPN server (no proxy here) and once you become part of the network, to use the proxy that is (likely) running on the same machine.
This is pretty much dependent on the OpenVPN client and the operating system you are using. The standard way for OpenVPN server to communicate to the client the use of a proxy server when browsing the web, is to push the message by adding the following lines to /var/ipfire/ovpn/scripts/server.conf.local (you need first to check the box “Additional Configuration” in the Web User Interface):
push dhcp-option PROXY_HTTP proxy_ip 800
push dhcp-option PROXY_HTTPS proxy_ip 800
Or in alternative you can add the following lines in the .ovpn configuration file that will be imported by the client:
dhcp-option PROXY_HTTP proxy_ip 800
dhcp-option PROXY_HTTPS proxy_ip 800
However, it is up to the operating system and the OpenVPN client to honor the request. For mobile devices, iOS will oblige the request, but Android does not allow a OpenVPN client to change the network configuration, therefore you will need to configure the proxy in android WIFI or APN connection setting that you will use when connecting to the proxy with OpenVPN connect client.
The proxy ip is the local ip, e.g 192.168.1.1
See my tutorial for a complete configuration howto for mobile devices.