The training week will offer an introductory program specifically designed for students and early-career researchers, with the aim of preparing participants who may not yet be experts on the topic for the main workshop. The school will focus on key cosmological observables relevant to the workshop, as well as methodologies for data analysis and statistical techniques used to compare theoretical models with observations. It will feature a combination of lectures, hands-on tutorials, and guided discussions. At the end of the week, students will also have the opportunity to present their own work and receive feedback from leading experts in the field. Dedicated discussion sessions will provide a valuable space for participants to engage with fellow researchers, ask questions, and potentially initiate new collaborations.