Neutrinos hold the promise of untangling many unresolved questions in particle physics. Their unique properties and behaviors offer a distinctive window into understanding the fundamentals of the universe, potentially providing answers to some of the most deep puzzles in modern physics. CEνNS, or Coherent Elastic Neutrino-Nucleus Scattering, is a process where a neutrino interacts with an atomic nucleus and scatters away, leaving the nucleus to recoil. CEνNS is an important area of study for understanding neutrino properties as well as their role in the universe. The COHERENT collaboration was the first to measure CEνNS, using neutrinos from the Spallation Neutron Source (SNS). The direct measurement of the SNS neutrino flux is vital for the precision of CEνNS measurements. This work introduces the latest addition to the COHERENT's armory –a D2O detector specifically designed to measure the SNS neutrino flux. In the present dissertation, the emphasis is made on the steps taken to operationalize COHERENT's D2O detector. This work unfolds the intensive simulation work directed to determine the detector's optimal design, ensuring it stands strong to the demands of neutrino physics experiments. Establishing the detector's calibration is essential to its operational phase. A dedicated calibration system, described in detail in this work, has been developed, utilizing encapsulated LED flashers controlled by a microcontroller unit to ensure the systematic and reliable calibration of the detector. A significant portion of the document is devoted to the calibration analysis, where we use Michel electrons to obtain an energy scale for the detector, thereby ensuring the reliability and accuracy of the future neutrino flux measurements. / Doctor of Philosophy / This dissertation delves into the fascinating world of neutrinos, subatomic particles that travel through space and matter, impacting the universe in many ways. Their elusive nature makes them a fascinating subject of study, as understanding them better can reveal more about the fundamentals of the cosmos. One process involving neutrinos is Coherent Elastic Neutrino-Nucleus Scattering (CEνNS), which is the main focus of the COHERENT experi- ment. CEνNS happens when a neutrino interacts with an atomic nucleus and scatters away. It is a vital field of study as it can provide insights into neutrino properties and behavi- ors, helping us explore many unanswered questions in physics. As part of COHERENT's experimental program, there is the need to measure the neutrino flux directly. This pre- cise measurement is crucial for ensuring the accuracy and reliability of the COHERENT's findings. To achieve this, COHERENT has introduced a new detector, filled with heavy water (D2O), designed to carefully capture and analyze neutrinos. This work outlines the extensive simulation undertaken to ensure the detector's effectiveness. Before the detector can successfully measure neutrino interactions, it must be carefully calibrated. This docu- ment also describes the construction of a unique calibration system, a critical step for the project's success. Finally, this dissertation highlights the development of a detailed calibra- tion analysis, an essential component for ensuring the detector's readings are accurate and trustworthy. This comprehensive preparation is fundamental for the next exciting phases of COHERENT's research into the mysterious world of neutrinos.