Hello, i'm a new finch owner and i LOVE them

I have two females in a large cage --- where can I buy males who are ready for breeding? I'm in the northeast of melbourne. When i get two males, should I just put them into the existing cage, or put them beside the cage in a separate cage first? And then should i separate the two pairs?
A bit scary, i don't want to stress them out!
and i am worried about the cold, one night i noticed they huddled and slept in the food tray, so i put them in a warmer room and they're clearly happier ---- what should I feed them exactly to make sure they have enough fat to sustain themselves???