Depends on the revolver. Some inexpensive guns had a removable cylinder pin- it would be removed, the cylinder could now be removed, and the pin used to eject empties. Older revolvers may have been "top break" guns- raising the cylinder latch permitted to barrel and cylinder to swing open on a hing, much like a double barreled shotgun opens.
If it's a modern revolver, you activate the cylinder release, open the cylinder, and push the ejector rod.
left side of revolver there is a small latch just behind the cylinder. pull the latch to the rear at the same time open cylinder
on the left side of revolver, behind the cylinder, there is a thumb device. for a colt the thumb device slides back to open the cylinder and on a S&W the thumb device is pushed forward to open the cylinder..............................
Open the cylinder its on the hinge closest to frame
Open the cylinder, it should be located near hinge.
You will either have to push or pull on the cylinder latch. If it doesn't have one, try to unscrew the ejector and see if that will free the cylinder.
A spring loaded ball detent holds the barrel/"cylinder" in place. Place your fingers on each side of the "cylinder" and push it out the right side with a rolling motion to open the action.
Open the cylinder and look inside on the frame where the crane assembly rests.
open the cylinder, and it should be stamped there along with the serial number
On a Colt revolver, the serial number is generally in two places. When you open the cylinder you will find the serial number at the base of the frame & crane.
If your revolver is an Iver Johnson Viking, it is a top break revolver. Holding the revolver in your right hand (finger OFF the trigger) use thumb and forefinger of left hand to grasp barrel latch (between back of cylinder and hammer) lift the latch, and revolver breaks open. If this does not work, take it to a gunsmith.
You have a single shot pistol which is built to look like a revolver. The cylinder is actually a breech block which is hinged at the bottom and pivots to the left, I think. Look for a small release button or lever to unlock the breech block.