The "People" category is automatically applied by the Add New Person Page feature within Add a New Wiki Page, so most users will not need to apply this category to any of the pages they create.
However, if a person page is created by any other means, then it is your responsibility to ensure the "People" category is applied.
It is for this reason that in the TRP Learning Series we suggest you do not click on any blue question marks following a child/parents name, since that presents a blank new page and not one which is appropriately categorised.
The "Search Wiki Page Names" feature in the right navigation column, with "Exact match" disabled, will return a list of pages whose page name contains the chosen search term. For example, a search for "Reeves_Charles" with "Exact match" disabled will return a list of pages which is a mixture of gleanings and person pages. By selecting the category "People" and clicking the "GO" button, the search results may be refined to show only those pages so categorised.
But recognise there is a small risk you may exclude a person page from your search results which hasn't been correctly categorised.