How to use decimal?

Excuse me, could you please elaborate on how to properly utilize decimals in the realm of cryptocurrency and finance? I understand they play a crucial role in precise calculations, but I'm a bit confused about their specific application. For instance, when making transactions or analyzing market trends, how do we ensure we're using decimals correctly to avoid any miscalculations or misunderstandings? Could you guide me through a step-by-step process or offer some examples? Thank you in advance for your assistance.