Gain kinah in the following ways

The common way in Aion Online to make kinah is to kill creatures. You can loot what the creatures leave such as materials and essences after killing them, and then trade them for kinah.
The second way is to do quests to make kinah. You are rewarded with prizes such kinah and items which can be traded for kinah, in completion of quests.
Players feel making kinah is boring in terms of killing creatures. it is in some degree, but it is very efficient, not only making kinah, but getting experience as well. As you proceed the aion game, you will be able to gain kinah in the game without any killing or questing, but maybe you will still want to stick to the methods of killing and questing since they can provide you with kinah and experience.