I installed NotifyOSD Config but I can't find the accessories folder in Ubuntu 11.10 where
notifyosd should be located.
Does anyone know where it is or how to open it?
The design of Unity trades ease of accessing any arbitrary application for ease of accessing a small number of "preferred applications". This means that browsing to anything but the most commonly used applications now requires a little more work.
To get a list of Accessories, you now must click Ubuntu button ▸ More Apps ▸ Filter results ▸ Accessories ▸ Installed: See more results.
In the case that you know what you're looking for ahead of time, though, it is immensely faster to use Unity's search function. Press Super to open the dash, then just start typing what you want. Enter will launch the topmost result.