How to use APK on Android box?

Could you elaborate on the steps involved in utilizing APK files on an Android box? Specifically, I'm curious about the process from start to finish, including any potential security considerations I should be aware of. For instance, is there a recommended way to obtain APKs safely? Should I be cautious of installing APKs from untrusted sources? Additionally, could you provide guidance on managing APK installations, such as updating or uninstalling them? I'm a novice in this area and would appreciate any clarity you could provide.