When you first arrive at the Documents section of Marty, you will be on a page that features a large list of the documents that ISS has on record. You can scroll through the list and click on a document's number to go to a page featuring that document's details.
Filtering
You'll notice that, right underneath the main navigation bar at the top of the page, there is a darker grey bar with some buttons ( All, NCF, WO, CL, etc.). We refer to this as the "filter bar". You can use the controls in the filter bar to limit the documents shown to only include those that match your criteria. The buttons for each document type are labelled with abbreviations. If you want to check what the abbreviation stands for, you can hover your mouse cursor over the button for a second or two, and you should see a label pop up.
You can also use the search bar ( the text input field next to a magnifying glass button) to filter the documents to only include those that contain the search term in their document number.
Note: Can't find the document you are looking for? You may want to check the filter buttons and the search bar. Perhaps a filter/search term is being applied that doesn't match your document.