Go to the auto parts store and get the little tool that removes the needle out of the tire valve, and a C-clamp big enough to clear the tire. Remove the the needle from the valve, it is about the only way to truly remove all the air, place the c-clamp on the tire as close to the rim as possible without touching it. I use a small peice of wood on the bottom side of the c-clamp to keep from scratching the rim. Tighten down the c-clamp, when it looks like the bead is about to let loose take a rubber mallet and hit the tire on each side of the clamp. It usually breaks pretty easy that way. Remove the clamp turn the tire over and do the same to the other side. Work your tire off using flat tire irons (you can use screwdrivers but they are not very kind to your wheels), usually when you get the tire a 1/4 of the way off it will pull right off of the rim.
When installing new tires I use dish detergent as a lubricant, spread it over the lips of the tires and press the tire over the rim, you should be able to get atleast half of it on by hand. This is where it gets difficult, ecspecially by yourself. You will need atleast 2 tire irons. Put your knee in the middle of the tire already on the rim, it needs to be about in the middle of the rim to give the other side enough room to stretch over the rim. Use your tire irons to work the rest of the tire over the rim, moving small sections of tire at a time sing the one iron to hold the previous accomplishment in place. The very last 6-8 inches is the pain in the a#$ to get on.
Things to pay attention to is cycle tire should only go one direction there will be an arrow pointing the correct direction for rotation. And there will be a dot or paint mark showing the lightest side of the tire, you want that to mark to be, where the air valve is in the rim. I have strips of plastic that I cut from milk jugs to place between the rim and tire iron to keep from scratching the rims.
I balance my rims by putting the axle through the rim and setting it on jack stands and spinning the wheel lightly, atleast enough for it to make 2-3 rotations, I then mark the bottom of the rim where it stops. Repeat this 3-4 times, the heavy side should be where it stops the most often.
Hope this helps some, it has saved me alot of money over the past 10 years on many bikes.