Something like this.
-(IBAction)PostToFacebook:(id)sender {
mySLComposerSheet = [[SLComposeViewController alloc] init];
mySLComposerSheet = [SLComposeViewController
composeViewControllerForServiceType:SLServiceTypeFacebook];
[mySLComposerSheet setInitialText:@"hi"];
UIGraphicsBeginImageContext(self.window.bounds.size);
[self.window.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
[mySLComposerSheet addImage:image];
[self presentViewController:mySLComposerSheet animated:YES completion:NULL];
}