Can anyone explain to me how to downtune songs? Like how bands get old and tune down 1/2 a step but it doesn't sound terrible, and when people cover songs and downtune. If you could explain this to me it would be very much appreciated.
you tune every string down the same interval and play like you normally would. Since everything is tuned down equally, the song still sounds in tune, it's just in a different key.

I don't really understand your question
"There he goes. One of God's own prototypes. Some kind of high powered mutant never even considered for mass production. Too weird to live, and too rare to die."-Duke
downtuning from a cover song is usually for the singer. when bands get old the singer can't hit the high notes like they used to *cough*led zeppelin*cough*COUGH*. that's why a lot of bands do alternate tunings in the first place.
yeah im guessing you dont know that much music theory Monolith?

listen to "All along the watchtower" by Bob Dylan then the cover by Jimi Hendrix.. thats a perfect example.. Bob uses "C" (that means standard!!!!) tuning and Jimi uses "B" (that means 1/2 step down!!!) tuning....