How configure apt-get with proxy

Question

I'm new one on elementary, I work behind a proxy. I cant get work apt -get behind a proxy , i tried to edit /etc/apt/apt.conf but i can't find, thanks for your help

Answer 1

finally i created a file apt.conf in /etc/apt/ , and i filled with

Acquire::http::proxy "http://:"; Acquire::https::proxy "http://:"; Acquire::ftp::proxy "http://:";

rebooted and it worked