Silly newbie question, but nonetheless...

I'm actually very new here, but I didn't tell you, but ok, ok.
This is a very beginner question and I feel really stupid asking this, but how do you get objects to enter and exit the screen? The way I am doing this now is by putting the object very far away and then getting it to move towards my center bit. However, I am sure there is a better way of doing it, because I keep losing track of where my objects are. Even methods for transparency will be welcome, as I don't know how to do that either.
Thanks for the help!

There are two ways to make an object disappear. Both are under the properties menu of an object. You can change the opacity to make it transparent, or you can change the "is showing" to make it disappear altogether.