All functions to create, reload and show fullscreen ads are included to RNAatkit module. So first you should import RNAatkit.
import {
RNAatkit,
} from '@addapptr/react-native-aatkit'
When AATKit is already initialized, you can create fullscreen placement. Just call createPlacement function passing placement name and the size as RNAatkit.PlacementSize_Fullscreen. Please note that the placement name has to be constant after once defined and cannot change with every app restart.
Then you can reload placement using reloadPlacement function. Also it's possible to let fullscreen ad be auto-reloaded by calling startPlacementAutoReload.