setting up users

I have read various threads with diffferent issues around this but I am struggling at first base in I am not sure I fully understand how access between users works, how folders are displayed on Finder, how different users can use programmes like Word, share iTunes, etc., how you can place icons within the dock for different users, how you store documents, etc. What is accessible through administrator account?

Can someone please point me to a simple guide which sets this all out for a simple sole?