These divine powers can only be cast on attacks. You can't cast them on your cities
These powers are -
Zeus' Rage/
Favorable Wind for Zeus;
Sea Storm for Poseidon;
Desire for Hera;
Heroic Power/
Wisdom for Athena;
Return of the Underworld/
Helmet of Invisibility for Hades;
Aim of the Huntress for Artemis. (green is for spells that give a bonus to the attack, red for malus)
To cast these powers, open the attack window (see screenshot below), go to the "Spells" tab, and choose which spell you wish to cast
To open the attack window, click on this: