Shove it under the edge of the hubcap and work all the way around to pry it off. Now, you can break the lugs. This takes some elbow grease. The only tip here is to grip the tire iron as close to the end as possible to maximize torque. The reason you do this before the car is jack up is because is would cause the car to fall off the jack due to the forces you will need to break out the lugs.
Most jacks are pretty simple, whether they're pneumatic or mechanical in some other way.
It shouldn't be that hard to figure out how it works. Jack the car up until the tire can spin freely off the ground. Now loosen all the lug nuts with the tire iron and place the nuts in the hubcap like a dish so you won't loose them. Lift the tire up slightly and pull it forward. Throw the old tire in the trunk and put the spare on.