How to set proxy with a config file provided in freebsd

I'm currently trying to update and install packages and other things on a FreeBSD server, but I’m blocked by my proxy. I'm in an university, and there are a few proxies before to go on the internet. To allow us ty bypass the proxy on our main PC (Debian 7) we need to enter the path of a config file in the networks settings (auto mode in proxy menu) But I can't manage to do this to my FreeBSD server. What can I get this to work?