If you're going to be changing tires, you'll need to break the existing beads into order to remove the old tires. Some give up the ghost easier than others, but all will require a bit (at least!) of applied leverage before they let go. Cars, motorcycles, tractors, etc. - they all work essentially the same. Even though a couple of these videos are motorcycle-specific, the principles are identical.
Tire Bead Breaker, Home made by Philippe Leblanc
Homemade Motorcycle Tire Bead Breaker by tearitupfixitrepeat
Homemade Bead Breaker For Motorcycle Tire by TEO WRF