Abilities and talents are unlocked through your class atlas. When you first start a class they will cost sparks of destruction, creation, and balance but once you class node they will be unlocked based on class sparks or evolution sparks. Class sparks are obtained through looting mobs in PvE while evolution sparks can be obtained from completing PvP instances or dropped form mobs in PvE. As you unlock more talents you are going to want more talent slots so you can equip them. Talent slots are unlocked through quests that will appear as you gain more prestige, be sure to finish all new quests! Keep in mind there are a total of 10 talent slots shown but you can only unlock 8 of them, the last two remain locked (for now!).