To assemble a window air conditioner, start by laying out the components like the front panel, filter, and mounting brackets. Using basic tools such as screwdrivers and pliers, attach the front panel and secure the filter in place. Install the mounting brackets on both sides of the unit, ensuring proper alignment with the window frame. Tighten all screws and fasteners securely to prevent vibrations during operation. Ensure the assembly is firm and all components are properly fitted before installation.