It used to be as simple as that Jelly, but it takes a lot of experience with such a weak light source to know what you are seeing. You are right on both points, it must not be too bright or very hot. There are some simple candling torches for sale, but avoid bright LED's, because the eyes of the embryo develop first and could easily be damaged. You would only realise your mistake if the chicks are born blind. There are candlers for sale that are very bright so that you can candle dark brown eggs, but don't use them for anything else.
The candling lamp is now placed to shine upwards into the egg and you view it from the side. You could simply use a torch if you used something to cover the light leaving only the area under the egg- easily made from cardboard in the shape of an upside-down cone with a hole in the small end to sit the egg on. Of course this exercise needs a dark room.
You won't see anything before 8 days and perhaps not until 12. The purpose of candling is to remove infertile or undeveloped eggs before they go bad and explode (they can) in the incubator, infecting all the other eggs. If the egg starts to 'weep', which can be seen as small crusty growths on the surface, take it out very carefully immediately.
Sure there are some pictures or sketches on the internet somewhere? I think I remember seeing something on the Brinsea site?
