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.
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: