SignUp.js

...
import auth from "@react-native-firebase/auth"
...

const __doSignUp = () => {
    if (!UserEmail) {
      Alert.alert('Error',"Email required *")
      return
    } else if (!UserPassword && UserPassword.trim() && UserPassword.length > 6) {
      Alert.alert('Error',"Weak password, minimum 6 chars")
      return
    } else {
      __doCreateUser(UserEmail, UserPassword)
      return
    } 
  }
  const __doCreateUser = async () => {
    try {
      let response = await auth().createUserWithEmailAndPassword(UserEmail, UserPassword)
      if (response) {
        console.log(response)
        Alert.alert('Welcome Message','Welcome the App');
      }
    } catch (e) {
      console.error(e.message)
    }
  }
  
...

onPress={() => __doSignUp()}