You can use Angular when your team knows Java, C#, and previous versions of Angular. Angular can be used when the application complexity is less. Angular can be used when you need an application with large-scale features.
You can use React when your team knows HTML, CSS, and JavaScript. React can be used when needing an application that is highly personalized for a specific aspect. React can be used for building an application with multiple events.
Visit Angular vs React to learn more differences about the two frameworks.
If you want to learn the Angular JS framework, I recommend registering for this Angular Training by Intellipaat.
You can watch this video comparing Angular and React to know when to use react and angular: