First touch equip or status in the menu with Gogo or Umaro in your party, then before you select a character in either sub menu quickly touch the back button and then touch where Gogo or Umaro would equip an esper (which is empty space). If done correctly you should highlight a blank box and go into the esper equip menu. Although neither can actually learn the spells espers teach, they can however gain the stat boost upon level up.