The quick search option is located in the bottom left corner of the application. Simply type your keyword into the field, then click on the magnifying glass or hit the Enter key. You will be brought to the word and the word will appear highlighted on your screen. You can use the up and down arrows to navigate between appearances of the keyword.
You can perform a more thorough search by clicking on the Binoculars icon in the auxiliary panel on the right hand side. Type in your keyword into the field and click on the New Search icon. Select your keyword from the list to be directed toward to it. You can clear the list with Clear All.
If you modify the document in any way, you will need to search again.