You will need to create an initial 192x192px icon and a 2208x2208px splash screen
The initial designs should be placed in the resources folder
The edges of the splash screen design may be cropped depending on the splash screen that is being generated, so you will need to make sure that important design elements are near to the center of the splash screen
Run ionic cordova resources to generate the splash screens and icons
You must have added the platform in order to generate assets for that platform, i.e. ionic cordova platform add android
You can also generate just the icons with ionic cordova resources -i or just the splash screens with ionic cordova resources -s
