Building an AI app involves several key steps. First, define the app’s purpose and identify the AI functionality needed, such as natural language processing or image recognition. Next, select appropriate AI frameworks and tools like TensorFlow or PyTorch. Develop the app's architecture, focusing on user experience and data flow. Collect and preprocess relevant data, ensuring it’s clean and well-structured. Train the AI model, test its accuracy, and integrate it into the app. After development, ensure robust security and privacy measures. Finally, test the app for performance, gather user feedback, and continuously improve the model and app features.