There are several videos of multi-piece wheel breakdown on You Tube. The main thing to remember is to get the tire completely deflated so the bead ring can be hammered or pushed away from the rim flange. The tire hammer with the spoon-shaped end on it is a big help here- - - -it is used to strike the tire sidewall just where it meets the edge of the rim, forcing the tire bead away from the flange. If you don't have a dismounting hammer, the base of a bumper jack or a high-lift jack applied to the tire sidewall and lifting against a heavy truck bumper or tractor axle is a good way to dislodge the beads.

Once the tire bead is free all the way around, tap the ring down and remove the split lock ring with a pry bar. Then the bead ring can be removed. Turn the tire/wheel assembly over and knock the bead loose from the other rim flange. The rim should be able to be removed from the center of the tire once the valve stem is pushed back through the slot in the wheel center into the tire. A strong solution of dishwashing liquid and water applied liberally to the bead area makes things slippery and helps the tire bead slip off the wheel. Once the tire is deflated there's no danger to a split rim- - - -the hazardous part is inflating it once the new tire is installed and the rim is assembled.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!