The first thing I'd say about EW is, if you're new to Zero Dark, skip this bit.
It affects only one type of specialist (the EWOp), so you may prefer to just build X Teams without an EWOp while you get used to the core rules. However, I would encourage you to include them as soon as you feel comfortable - especially in the PvP game - as they open up a realm of combat that is entirely new.
In the setting, Electronic Warfare Operations (EWOps) have embraced the language of gaming and talk happily about "casing", "spelldecks", "familiars" and suchlike. To take the analogy further, there are two broad categories of "spell" that the EWOps can use:
Buff spells are used on allies to make them better. You can remove nasty conditions, like targeted or impose useful ones, like support tokens or an enhanced firewall. The other thing you can do with a buff is change a friendly robot's program.
De-buff spells, meanwhile, are used on opponents to inflict bad conditions or remove useful ones, opposite to the above. They can also be used to change enemy robot's programs! But de-buff spells also provide the ability to enter the "interference" state.
Interference represents the EWOp diving into the enemy BattleNet to steal information and mess with their plans. An EWOp in the intererence state can do a range of special actions: attacking enemy EWOps in digital duels, messing with the control deck or hiding one of their allies from being easily perceived by the enemy BattleNet.
Domination is one of the most fun - but also most tricky - sides of electronic warfare: attempting to wrest control of an enemy synthetic from its own BattleNet. It's quite a conditional action - and I got the rules wrong myself in one of the recent livestreams! The target has to be in the targeted state with no support tokens, the attempt must be declared in advance as a dominate action and the domination cannot generate bonus actions.
The idea behind this is that, in PvP games, your opponent is going to notice that you're trying to dominate his synthetic (just as the BattleNet would notice such an action) and have the chance to stop you. If you want to dominate an enemy synthetic, the first thing you would need to do is make sure the enemy EWOp can't stop you by, for example, engaging them in a digital duel...
Dominated characters retain all of their state and upgrades, but now they work for the enemy! Dominated bogeys, meanwhile, get a new statline of their own. It's not as good a statline as a hero's going to have, but that reflects how much easier it is to dominate a bogey than a character in an opposing X Team.
Anyway, I hope you get a sense of the role that EWOps can play in Zero Dark. They really are the spellcasters of the scifi world, using their skills to protect and enhance their allies and to confuse and harrass the enemy.
I hope to expand on the options for EWOps in future supplements but, for now, I think they are more than adequately complicated, whilst still being a fun and characterful addition to the game.