The simple button...

[SLi78]

Unfortunately the button isn't a real entity with which you can interact.
Therefore you have to make your own button with the model editor.
Just load it up in the model editor and then under the menu "Settings"->"User defined variables" change its Type from "Object" to "Button".
Then save it under another name in the same folder.
Now you can use your new, useable button.

thx

it works, but as far as i see is there no animation for pushing the button, so i use a lever now.