Maybe you didn't get any answers because your question is so amateur and not organic specific. Don't take that as an insult please I just mean that in this particular thread I think people are working mostly at a higher level so when someone calls coconut coir "soil" they just don't feel like giving someone a day 1 lesson- add to that the fact that if you tell someone to use the Canna Coco fertilizer with the Canna Coco coir then that's not at all organic.
*'Canna Coco' is not "soil"- if by soil you are referring to some kind of potting mix or the earth in your back yard. It Canna Coco is 100% Coco coir, which is made from the husk of coconuts. It is technically a hydroponic material because if you grow using it you are soil less. It can be used by itself or added to a potting mix for a similar result as adding peat moss. One of it's pro's as a stand alone media over rockwool is higher oxygen holding capacity.
*By itself out of the bag, it's very near to inert. A simple way of looking at it is that it's a material where the only fertilizer that is in it- is what you put in it, just like rockwool. Beware of salt build up though. You should determine a regular flushing routine such as once a month give it a big flush or some people do one water fertilizer one feed water alternating.
*It breaks down but not before the end of a single grow. As it breaks down I think it releases a little bit of phosphorous. Generally people will only use it once and then dump it to start new for the next grow.
*You can use hydroponic fertilizer, coco specific 'hydroponic fertilizer' or some people use bottled organic. Apparently it has calcium and magnesium problems at times so some brands sell a supplement for that you can add. The main difference between the Canna regular hydro fertilizer and the Canna Coco is Fulvic acid which helps nutrient availability. Not sure if Humic acid is in it too but that would also help.
So to specifically answer your question now- you start fertilizing it the same time as you would if it were in rockwool or any other hydroponic media... which is not immediately but start a quarter strength fertilizer once the seedling is established and about to start growing into a little plant. If you start light and read the leaf colour the you'll be safe.