Over the past couple of years, Fedora has replaced YUM with a re-written and tidied-up version (
) called DNF. DNF's configuration file is /etc/dnf/dnf.conf, but the options are largely the same as were used in yum.conf.
You can check the commands as there is a manual page for this configuration file - enter "man dnf.conf" - but these are the lines that you are probably interested in
URL of a proxy server to connect through. If none is specified then direct connection is used (the default).
The username to use for connecting to the proxy server. Empty by default.
The password to use for connecting to the proxy server. Empty by default.
If I remember, the above are unchanged from yum.conf.