Insignias are the symbols of Gods and Goddesses of eridian 59 that one can have emblazoned on their Herald Shields. To acquire one, travel to the teacher of the desired symbol (for instance, if you want the Shal'ille symbol, head to that school) and say..

You say, "May I wear the insignia of the Goddess/God on my shield?"

After you make your comment to her she will say,

"That I noticed you don't have an crest on your shield, and she could put the Goddess/God insignia on as if you pay her a tithe."

Say "tithe" and then she will give you a task to complete, something roundabout and annoying, normally. Complete the mission and go back to her.

Upon returning, simply prompt her by selling hello or whatever and she should reward you.

While there is no 'tithe' quest for Jala, one can procure Jala herald shields from the chest in Castle Victoria.