To apply DFA, designers need to follow a systematic process that involves four steps: analysis, evaluation, improvement, and verification. In the analysis step, designers need to define the product requirements, functions, and features, and then break down the product into its components and subassemblies. In the evaluation step, designers need to assess the assembly difficulty, cost, and time for each component and subassembly, and calculate the assembly efficiency index (AEI) for the product. The AEI is a ratio that measures how close the product is to the ideal assembly condition, which is one part with one operation. In the improvement step, designers need to apply the DFA principles and guidelines to simplify the assembly sequence, such as reducing the number of parts, standardizing the parts and connections, minimizing the handling and orientation, and facilitating the insertion and fastening. In the verification step, designers need to test and validate the improved assembly sequence, and compare the results with the original design.