For every 500ml you add half a tsp for ales porters (etc) and a full tsp for lager and cider.
If the bottles are clear keep them out of any sunlight as this can cause the brew to skunk giving off fusty tastes.
Also the yeast will have used all the added sugar up after only 1 week in the bottles, you will be able to tell this by squeezing the bottles and they should be firm to the touch.
As for not having to add sugar to the bottle to carbonate it, well thats actually wrong, if you fermented the brew out correctly the yeast will have used up all the fermentables and will have given you a constant hydrometer reading over 3 days adding no more sugar will still give you a nice tasteing brew as it will condition in the bottle but it will be flat.
Andy
Thank you Andy, this useful!
After trying three bottles, as Auntiemogs says, they were all still unprimed, and pretty well flat.
I'd topped them up with water, and tried again, but no avail, so I've now undone all the bottles, mixed them all again with some new yeast, and it seems to have restarted in a limited way.
I'll take your advice on the teaspooing, and will try two per two-litre bottle.
Its a strange one this, as it's such a basic recipe, (I'll post it Auntie - promise...), there shouldn't really be a problem! It tastes just like a strong stout, but is not lively enough!