The document provides guidelines for designing science education learning activities using the COSMOS Authoring Engine for Learning Activities (COSMOS ASK-LDT). It describes the main functionalities of COSMOS ASK-LDT, which allow users to create new educational scenarios based on predefined templates, populate learning activities and environments with educational resources, and generate IMS Learning Design compliant packages. A step-by-step authoring process is outlined, along with examples of designing scenarios aligned with different pedagogical models.