Cock the hammer.

Open the side cover and, while rotating the cylinder, load it with cartridges through the open port (ensuring that the side with the gray compound faces you and the notched end points in the direction of the shot).

Close the side cover.

While rotating the cylinder, align the cartridge with the firing position at the special notch.

Make a shot, then cock the hammer and align the next cartridge with the firing position.

When all cartridges have been fired, cock the hammer, open the side cover and use the spring-loaded ramrod to clear the cylinder of spent cases.

Kindly watch the video of the Colt 1873 Peacemaker Revolver (Scale 1:4) in action:

Be sure before use to read the safety rules here.