A collection of common antenna design tools can be found eg: Yagi, Log Yagi, Horn, Helix, Corner
In essence just a collection metal arrange in space in such a form to match the drive source into the ether either via the electrical field or the magnetic field coupling. The exact arrangement of the pieces of metal decide if all this RF power we are emmitting goes to all and sundry or just to jenny cornfield sitting on top a hill in way yonder.