Step 1 : controller

                     import 'package:flutter/cupertino.dart';
                    import 'package:get/get.dart';
                   
                   

                    class BranchController extends GetxController {
                      @override
                      void onInit() {
                        super.onInit();

                         

                      }

                      updatePanel() {
                          
                      }


                    }

                    

extends from GetxController

Step 2: UI

                    import 'package:flutter/material.dart';
                    import 'package:get/get.dart';
                    import 'package:getx_restaurant/controllers/branch_controller.dart';

                    class BranchScreen extends StatelessWidget {
                      BranchScreen({Key? key}) : super(key: key);


                      @override
                      Widget build(BuildContext context) {
                        Get.put(BranchController());
                        return Scaffold(

                          body: Center(
                            child: Text(
                              'Add',
                              style: TextStyle(fontSize: 20.0),
                            ),
                          ),
                        );
                      }
                    }


                

Step 3: define route in main.dart

                 import 'package:getx_restaurant/screens/branch.dart'; 

                 .... 
                 .... 

                 getPages: [
                    GetPage(name: '/branch', page: () =>  BranchScreen())
                ]
                 
                

Step 4: call route

onTap of button in side_menu.dart

                onTap: () => Get.offAndToNamed('/branch'),