How do you add something to a disk image?

Hi There

I have just learnt how to lock a folder by using disk utility. But now I can't add anything to the folder. I have tried to drag and drop the folders but nothing happened. Did I do something wrong in the process? Is there another way to add things into a disk image?

The only way for me to do it now is to delete the dmg file and create a new one.

If it is impossible (or just not simple enough), can someone please tell me another way to lock a folder, and if it is possible, to lock the folder directly without creating a new file.

thanks

You must of created a read only disk image. Try again but set it to read write in disk utility

Oh thank you so much! But is there still a way to protect ANY file or application directly?