Here are the things to do in becoming an Assist:
1. In Flaris, you have to kill mobs such as Aibats, Puke - Puke, Damien, and the toughest could be the Nyang nyangs to reach to level 15. Try to collect Forforms at this stage for future purposes trust me.
2. Meet Assist Drillmaster Ellic in Eastern Flarine. He will give a job quest that will require you to kill 10 small Aibatt. Please take note that small Aibat is different from other Aibats.
Every quest will be held here in Flaris
3. Go back to Drillmaster Ellic once you have killed all 10 small Aibats. He will now give you another job quest. This time you will kill Muspangs to get Forforms. (if you have collected enough Forforms in step 1 it'll be easier for you)
4. At this stage you must have been familiar with the High Dwarpets in the Billeting Place. Now you will have to talk to Goripeg, your job quest now requires you to kill Chaner (the red scorpion near damiens) in Madren Town. Get the Label of Technique from Goripeg once it is done.
5. Now bring the Label of Technique to Kidmen Nicore the Assist Instructor (why do I think of an actress every time I see this NPC). She is located at East Flarine. And she will bless you and you become an official Assist of Flyff. Have fun!!