To trace an O2 molecule from the air to the right arm, what does it have to travel through.?

I know it travels through the respiratory system and the heart, but does it go to the left lung first or the right. and does it go into the right side of the heart of left. I'm so confused.

There are 3 main components to the circulatory system. The muscular pump that is the heart, and the two main pipes, arterial and venous circulation. There are 4 chambers in the heart, and I'll label them as such:
12
34
That signifies the top/bottom, left and right chambers of the heart. Atria are the top half, and Ventricles are the bottom half.
Oxygenated blood flows from #4 releasing oxygen to organs and tissues at capillary beds. At this point, the blood is now CO2 rich,and travels through the veins back to #1. Then it flows from #3 to the lungs where gas exchange happens again, this time the blood is releasing CO2 and taking in O2 from the lungs. It will end up at #2 and the whole cycle will start over again.

The air (oxygen) enters the nose and or mouth into the trachea. From here it enters the bronchi, bronchioles and finally the alveoli of the lungs. Here it will diffuse into the blood and attach itself to the hemoglobin molecule in the red blood cells. This newly oxygenated blood will leave the lungs via the pulmonary vein and empty into the left atrium of the heart. From here it will move into the left ventricle which will pump it out of the heart via the aorta. The aorta will branch into the subclavian artery delivering the blood to the right arm. From here it will divide into arterioles and finally capillaries reaching all the cells.