You can search for documents from 2 places
1. From the dashboard you have a search field in the top left corner, here you can search for exactly the document name, part of the name or document ID. Insert the search criteria and press enter.
You will now see a list of documents with the word Test in the title
You can also set a filter to not search in all documents by clicking the filter button and make the filter choice.
2. In report index you also have a search field. Search in the report index will also search inside document content and will most probably give you a different output than the search on dashboard.