The Search function is located in the top right corner of the Header in the Main View.. 

Type in your query in the light green text field and click on the SEARCH button to open a Search Detached View listing all the found matches. The query is case insensitive, and you can type in one or several words, each separated by a space.

You can also directly click on the SEARCH button to open the Detached View and launch your query from there.