Adding Objects at a later point of the scene

Hey it’s me again.
Ok here is my question. When I animated a scene I wanted to make an obejct appear at the 4th key frame for example. But when I tried to do so the object remains at the origin from the first frame till the frame I wanted it to move. Is there any way of adding object during a scene ? I also tried to uses overlapping layers or moving the object from the margin of the screen but none of it worked. Sorry for my rather bad English but I just do not know how to say this but thanks in advance.

Look at this thread, it may help you ^^ :

oh thanks, I’ve been looking 2 days for that topic.