Safety-critical systems are subject to rigorous assurance and certification processes to guarantee that they do not pose unreasonable risks to people, property, or the environment. The associated activities are usually complex and time-consuming, thus they need adequate support for their execution. The activities are further becoming more challenging as the systems are evolving towards open, interconnected systems with new features, e.g. Internet connectivity, and new assurance needs, e.g. compliance with several assurance standards for different dependability attributes. This requires the development of novel approaches for cost-effective assurance and certification. With the overall goal of lowering assurance and certification costs in face of rapidly changing features and market needs, the AMASS project has created and consolidated the de-facto European-wide open solution for assurance and certification of critical systems. This has been achieved by establishing a novel holistic and reuse-oriented approach for architecture-driven assurance, multi-concern assurance, and for seamless interoperability between assurance and engineering activities along with third-party activities. This paper introduces the main elements of the AMASS approach and how to use them and benefit from them.