If I want to add more sticks, do I need to add a worker for each stick? If so how do I add the new workers to the mine?
No, bgfminer will detect all sticks, they will show up as MLD0, MLD1 and so on. Only one worker (you specifiy that in the bat file). It is possible to assign a specific stick to a worker but I gather from your question that that is not what you want, therefore saving you what to do to get that. It is all in this thread somewhere.