u dont have to "use" it, u have to "put" it as main eido in ur first A-F parties, and it should be first light main eido in list

i.e. lets say u have 6 teams for each element, and light is... idk, fifth. means u have main fire/wind/etc eidos on prev teams, and mana on ur 5th
ppl will see ur mana when they switch to light support