Hi Andy. Welcome to G2G!
According to FamilySearch, GEDCOM files cannot be downloaded directly. See this link.
However, you can use a partner software program which can extract the data from FamilySearch then create a GEDCOM file. The partners are listed at this second link.
I believe that for this purpose the listing of WikiTree itself on that page is an error. WikiTree cannot extract data in bulk from FamilySearch. Maybe other people who have used some of the other software programs listed can make recommendations.
Edited to add: The WikiTree Sourcer browser extension by Rob Pavey can extract information from FamilySearch, but this only works for one profile at a time, and does not involve a GEDCOM file. Nonetheless, that might help to explain why WikiTree appears on the above-mentioned FamilySearch page.