You would actually need to find out the Category before adding one in. WordPress doesn’t always name them 1, 2, 3, 4 and so on….sometimes the numbers can be anything, like 120, 249, 360, etc. WordPress has a Categories page under “Posts” in your admin. One way to find out is to hover over one of the categories and look at the link….or you could copy the link paste it somewhere and then look at the link. You should see the ID of the category inside of the url. Let me know if that helps.