Players Currently Within the 30-Day Free Trial Period
Players who began playing as of May 2012 and have registered for a 90-day period before June 30, 2012 will be able to fulfill the requirements needed to qualify for the Legacy Campaign.
You need to have started playing before the end of May, and you must sign up for the 90-day subscription before the end of this month. If you didn't register in May then you unfortunately can't qualify at all.