It's wise to have a good mix of different Keywords created to drive traffic to your Ads.  Remember, a Keyword belongs to an Ad Group, so when a searcher on Google® or Bing^TM searches with one of your Keywords, any Ad in the Ad Group the Keyword is associated with could appear to the searcher.  To create more Keywords, from the "Manage Campaigns" tab, select a Campaign, then an Ad Group in which you wish to create new Keywords.  In the Keywords section, there will be a link named "Create New Keywords" that will help you.