title: GKAchievement (Game Center) showing?
body: <p>this is a likely silly question. But I added Game Center to my app and now I want to add achievements, too. So I created a test achievement on itunesconnect and copied this method:</p>
  
  <pre><code>    - (void) reportAchievementIdentifier: (NSString*) identifier percentComplete: (float) percent {
      GKAchievement *achievement = [[[GKAchievement alloc] initWithIdentifier: identifier] autorelease];
      if (achievement)
      {
    achievement.percentComplete = percent;
    [achievement reportAchievementWithCompletionHandler:^(NSError *error)
     {
      if (error != nil)
      {
       // Retain the achievement object and try again later (not shown).
      }
     }];
      } }
  </code></pre>
  
  <p>But what do I have to do now. Where do I have to write the code that says that the achievement is reached? Where do I have to write the code that says that the achievement is reached by doing this?</p>