To attach a script to an entity you place the entity, then right-click on it and you will get a list on the left of all the entity's properties.
Now look for the properties called 'Start', 'Main' and 'Destroy' in the 'AI Scripts' heading.
Now you need to decide when you want the script to be run; you can have it run when the entity is created(Start), when the entity is destroyed(Destroy) or have it running all the time(Main).
Click on the option you have chosen and a little button will appear to the right of the property.
Click the button and a browse window will open, select the script you want to set and then click 'OK'.
Theat script will now be set to run at the time you chose for that entity.
See attached picture for where the 'Ai Scripts' properties are and where the 'Browse' button is.
knxrb