In order to obtain this Trophy you must activate 20 different nodes in the Ascension menu.
To unlock nodes you will need to gain Ability Points, this can be done through a variety of ways.
Defeating an enemy with a Warp Strike will reward you with a single Ability Point each. In turn, defeating enemies and completing quests earns EXP and when a character reaches a new level you are rewarded with 3 AP. When you set up a camp you have the option to Train with Gladiolus which when completed earns you 5 AP each tier.
Playing the game normally should provide you with enough AP to activate this many different nodes around Chapters 3 or 4. Once you have activated your 20th node the Trophy will unlock.