If you're referring to the splash screen that appears as your app starts up on Android and iOS then it is displayed while your app is starting up. If you want it to go away faster then you need to speed up your startup process.
Since we have no way of knowing what your app is doing at startup we can only guess at things to speed it up. A common slowdown at startup is attempting to load the initial set of data needed by the main view. To make this faster move that logic into async calls that occur after the main view is shown. Unfortunately this isn't much help to the user since they will still not be able to do much with your app until your data loads in many cases, but it depends on your app.
Other slowdowns could include loading external resources like images or connecting to shared resources like the camera. Anything you can move out of the startup time will help. Note that you'll always have the overhead of loading the app, starting the runtime, etc and there isn't much you can do about that.