Tieing Things Together?

This is the outputs to a trigger_multiple which is tied to a func_door.

So you name your entity (the door) - and then put the in outputs the doors name with the command you want.

Please read the article I linked over in your other thread, it explains pretty much everything you need to start mapping.

Do you mean tying a brush to an entity? That term confused me too when I first started. Create the brush, then click "To Entity" on the lower right toolbar. The brush is now a func_detail. You can then change the class using the drop down menu in the window that pops up.

Example of "Tying" a brush to a trigger:

Make a brush with the block tool textured with the trigger texture.
With it selected, click "To Entity." (I think Ctrl+T also works, but I don't remember).
Change he class name from func_detail to trigger_multiple.

Edit: Correct key combination

Tie to entity is ctrl-t; move to world is ctrl-shift-w.