When a Word, Excel or PowerPoint file has been filed in FYI, you find the documents within FYI and open them from there. This will launch the relevant Office program.
The Office program will either open in Office desktop or Office online depending on or default settings, or on how you select to open the document.
Refer also to Opening, Editing and Finish Editing Documents and Setting Defaults and Filing Defaults for your Own Login - My Settings.