The choices of different operations you have depends on the specifications of the race you chose at the registration of you empire. You also chose a magic race bonus then, varying from -30% (custom) to +70% (Partaxians). Note that these boni/mali count for both defense as well as offense!

Supply the required coordinates for the planet owned by the empire that you wish to attack and select an agent and/or magic operation.
Note that if you reached the Spec Ops from the map the coordinates are already given.
You should also enter the amount of agents of mages to use.

The spells that are self spells are friendly and casted against yourself. If you want to perform one of those you don't need to supply any coordinates.

The factors determining the success of your op/spell are:
* the difficulty of the op/spell
* your NW
* amount of agents/wizards you send
* your magic bonus (magic spells only)
* a probability factor
And in case its no self spell but a spell casted against an enemy target or an operation performed on an enemy target:
* your enemies NW
* amount of agents/wizards your enemy has
* your enemies magic bonus (magic spells only)
NW only plays a role when you op someone smaller then you.

After performing the op you'll see whether you succeeded or failed. Note that with every failure you'll lose 5% of your agents or wizards.
Click this link to see the list of avaliable operations.
The only way to protect yourself from spells/ops is to get a sufficient amount of wizards/agents as a defense.