In this detailed, step-by-step guide, we will show you how to install the Debian 12 (Bookworm) operating system in UEFI mode with the lightweight and fast XFCE desktop environment. We will use the user-friendly Calamares installer available in Debian Live for installation. The guide will guide you from downloading the appropriate ISO image and creating a bootable USB drive to booting the system for the first time. We will put special emphasis on manual partitioning, where we will create the EFI, root, and swap partitions required for modern UEFI systems in detail. The entire process is illustrated with plenty of screenshots so that even novice users can follow the steps with confidence. By the end of the guide, you will have a fully functional, stable, and ready-to-use Debian 12 system.