The library catalog uses Library of Congress Subject Headings. The list of authorized subject headings is available online from the Library of Congress Classification/Subject Headings database. However, you can also start with keyword searches to gather some relevant titles, then look at their subject headings to discover the official terms to use.
The Library of Congress Subject Headings for Fascism and Antifascism are:
Under countries as subjects, you will find many chronologic subdivisions corresponding to major events in that country's history. You will also find separate headings for specific events.
Also consider keyword searches on personal names relevant to the fascism and antifascism. Typically, names are entered with the last name first, e.g., Mussolini, Benito. Do both Author and Subject searches to find books by and about the individual.