Assumes that you have completed all the pre requisite steps provided in the article: How to Create and Configure People Search Application
People Search Capability
People Search provides users the ability to instantly search for coworkers from any page, with enhanced results that are filtered in real time and the user types.
To use people search, simple ensure the "People Only" option is checked on the search box at the top or the page and begin typing your search.
As soon as two or more characters have been entered into the Search box, a list of matching results will be returned displaying the Thumbnail image, Name, Title, Email address, Phone Number(s), and Location. Continue typing and the results will automatically be filtered in real time to match your new query.
When no match/results can be found, a "No results" message will be displayed.