function openDBFfile(filename : String): Boolean;

This function opens DBF file. It accepts a string and returns a boolean value, true if everything was good.
Do not forget to close your file if you do not need it anymore.

var
    dbf: TcdbfapiPlus;
begin
    dbf := TcdbfapiPlus.Create;
    if (dbf.openDBFFile('c:\tmp\example.dbf')) then
    begin
        // your code
        dbf.closeDBFFile;
    end;
    dbf := nil;
end;