To get in on the deal, head over to the WOW Air site and peruse your options. But you'd be wise to do so quickly, since the across-the-board $129 one-way flight offer is limited to 5,000 seats and will be gone once enough people book them. It's also worth noting that while the outbound flights are crazy-cheap, many of the return flight options are significantly more expensive. Then again, you don't necessarily have to fly back on WOW.
Of course, as with most budget airline sales like this, there are some restrictions and fine print to consider before you pull the trigger and book anything. For instance, these deals are good for WOW "Basic" fares, which don't let you pick your seat and only allow you to bring a personal item. If, like most people, you plan to bring more than a backpack or purse abroad, you're going to have to pay an additional baggage fee for any carry-on or checked luggage (which varies depending on your route). Also, every WOW Air flight has a stopover in Reykjavic, so unless your final destination is Iceland, you won't be flying non-stop. That said, a brief layover and packing restriction are more than worth scoring a trip across the Atlantic for under $150.
And just in case you need any more arm-twisting to take advantage of a bargain European excursion, you're welcome.