I have placed lots of Light sources like braziers , candles etc , but they do not emit any light around them I am missing something obvious I guess but I couln't guess what ... any ideas?

Not sure I understand your question correctly:
Lights can be located in the Object Window, in WorldObjects > Lights. From here, they can simply be dragged into the Render Window, just like static art.

I mean, first you place the candle then you add the light fx that emits light.

Cheers!

The model (the braziers and such) and the actual light source are different objects. The lights are found under WorldObjects/Light.

Yeh I found them but they do not project much light , seems that the normal portable torches use the same radius of 512 m as the big braziers wich cast few light , also is there any setting tomake those lights cast shadows or this is automatic?

you can hold down s and drag your mouse to make the light brighter/dimmer (while its selected and you have the quad arrow over it). There is shadow lights, if you place a light and it has a pink crossbar in the middle it is a shadow casting light. Best advise would be to watch the lighting tutorial videos, lots of them in the http://www.gamesas.com/topic/1343653-creation-kit-video-tutorials-merged/ on main page.

oh ok cool , its safe to use the shadow lights in exteriors? or they are resource consuming or the like?

not sure if they woudl cause any mess ... so far I used the same ones used in vanilla regions ....

double...

not to sure how much of an impact it would have on performance in the outside cells, I havnt dabbled with them much yet. I have been working on a large interior cave, its a pain getting lighting to work right.

Remember that you can have only 4 shadow casting lights being rendered on screen at any given time. Having all of them in close proximity can incur some performance hit.

^

just make sure you take a look at the vids, some very good info even if you just skim through to get the gist of whats going on. I have found most of my answers from the variety of tutorial vids available.

Ok so I may use them for braziers at least , they are scattered around the city I may have lik e10 in total more or less and at the max I should have a couple per cell ...

yes, you could also try implementing http://skyrim.nexusmods.com/downloads/file.php?id=10361 to add more shadow casting lights to issgard, (especially since your mod is city based and most of them can be put out of line of sight of each other)