A family of Microsoft word processing software products for creating web, email, and print documents.
Please disregard the reply from the so-called "advisor" identifying him/herself as gems888. This has nothing to do with Font Book & such a response suggests that the individual doesn't even know what a cloud font is. In fact, none of the Microsoft fonts supplied with Office 365 [cloud or not] are managed by Font Book. Font Book is used for installing fonts obtained from other sources.
Microsoft cloud fonts are not installed locally as described in that article but are retrieved from an internet server [i.e., cloud]. They are cached within a local Office folder. There should be no reason to download or install them.
In order someone to assist, please go to Word> About Microsoft Word to determine the specific Version of your Office software. Include that as well as your version of macOS in your reply.
Also, please indicate exactly which font(s) you are referring to. Cloud fonts are available from a variety of sources: Are you sure the fonts you want are from Microsoft rather than Google, Adobe, or some other source? Provide as much descriptive detail as possible.