Add Instant Search Fields

Customize Search Fields

Click inside the Search Box in the Title Bar (NEW LOCATION)

Select Current Mailbox

(The Search Tab in the Ribbon will also open)

Select +Add More Options

Check the box next to your preferred options; Uncheck to remove
Select Apply

Each item will be listed in the Current Mailbox window when you click Search > Current Mailbox again
Narrow down your searches using the fields in the search window