I'm just learning Fedora myself, though I have used SuSE for years.
My impression is that yum looks on the internet to update and install files and pirut which adds/removes programs grumbles if it doesn't have an internet connection.
If it is asking you for a baseurl, it DEFINITELY wants to connect to an internet (URL) address. So you have to set this up first.
If using KDE try kinternet, I'm not sure what the equivalent command line is in gnome. As I use a proxy server with fast internet cable (flatmate is elec.engineer and can't survive without this apparently!), I'm a bit rusty on dialup setups. If you have installed gnome, I'm afraid you are on your own as I don't have a PC using it at the moment.
Maybe someone else can help?
Anyway, stop doing this and get on with Christmas cheer etc.
Best wishes for New Year.