1// add this line at the top before #import "AppDelegate.h"
2#import <React/RCTI18nUtil.h>
3
4//add this line to the didFinishLaunchingWithOptions method before return YES
5  [[RCTI18nUtil sharedInstance] allowRTL:YES];
6  [[RCTI18nUtil sharedInstance] forceRTL:YES];

1add two below codes to App.js => 
2I18nManager.allowRTL(true);
3I18nManager.forceRTL(true);