Understanding the spin structure of the proton, specifically how its quark and gluon constituents contribute to its overall spin, remains a key challenge in modern particle physics. These contributions can be explored in high-energy scattering processes involving polarized nucleons, with polarized deep inelastic scattering (DIS) being one of the most important probes. The future Electron-Ion Collider (EIC) will allow for unprecedented precision in such measurements, triggering the need for predictions that match that level of accuracy. In this seminar, I will present a new Monte Carlo event generator for polarized DIS at next-to-leading order (NLO) in QCD, incorporating parton shower effects within the POWHEG framework. I will describe the necessary extensions to handle polarized initial states and show predictions for the kinematics of the upcoming EIC. Before discussing the methodology and results, I will provide a brief introduction to polarized collisions and the proton's spin structure.