Search for a file or keyword in the main search bar at the top of the website by typing your term into the search field and then pressing return on your keyboard or clicking the icon of the magnifying glass. [pictured below]
You will be shown a list of results. These results are from all Box files. Not specific to Insigniam Sales Documents. Narrow your search in Step 2 below.
Narrow the search results specifically to Insigniam Sales Documents by clicking the "Any Folder" drop down menu on the right, and drilling down to Insigniam Sales Documents [as pictured below] by clicking on the drop down arrows to expand the folders.
Once you've located the specific folder you'd like to narrow your search by click on it to load the new results.
That's it, your new results will now be narrowed down to just that folder, including that folders subfolders, as pictured below.