To enable Multiple Search the multipleSesrch option should be set to true in navigator search options.
Searching (or also sometimes called "Filtering") is supported through the Search Button option off the ToolBar. This will bring a search dialog with common operations (equal, less or equal, greater, not equal, contains, etc).
You can control the various aspects of the Search Dialog via the searchoptions array and navigator search options.
If the data is loaded via array or string - i.e local data - the search is performed automatically. If you use server side data you will need to build your own search procedure at the server.