Use the Advanced Search Tab
With the advanced search, you can search on more specific terms, including by author, workflow, milestone fields, and templates.
Advanced Search using a Keyword
In order to find items which have used a certain keyword, you will need to perform a search. To do this, use the search bar at the top (ensure this is set on the advanced search tab). You can enter your criteria as normal in the various fields, but please note you will now see the keywords picker. Within this window, you can choose the Keyword(s) you wish to include in your search criteria.
When searching, all Keywords are shown by default. This is to allow cross project searches, however, assigned keywords to that level are displayed in bold. A user can also use the check box to toggle between an AND search or an OR search. If this box is not selected, items will be returned as long as they contain at least one of the Keywords you have selected.