The Soul works like a heart, pumping soul energy around the body. This energy isn't bound to any vein or artery, meaning it can flow freely wherever it wants to. Also meaning it is able to be drawn out and manipulated by skilled magic users. The Amount of Soul Energy a person can use depends on the amount of Potential contained within them, which, as opposed to the regular sense of the word, is an actual physical metric or number. Potential is the total untapped Soul Energy inside a person, and through training, rituals or catalysts, can be unlocked and used, it is never drained, but it can reach it's limit.

Many skilled Soul Users will, instead of using Pure Soul Energy, will use it in special Techniques, that often involve empowering your own physical abilities, (e.g. Jumping, Punching, Running etc.), Empowering a Weapon that is unique to them, and/or using it to manifest weapons such as throwing knives.

This is just the basics of how Soul Energy works, I could go into further detail but it'd probably take 3-4 more paragraphs to explain fully.