Form1 is a type but used like a variable [on hold]

I'm having a problem accessing my ListBox1 inside a class.

public static void LoadLists(Form1 f1)
       {
           string path = "//Employees.meta";
           var doc = XDocument.Load(path);
           var items = doc.Descendants("Employees");
           var query = from x in items

                       select new
                       {
                           Name = (string)x.Element("Name"),
                           Gender = (string)x.Element("SubData")
                               .Element("Person")
                               .Element("Gender")
                       };

           foreach (var item in query)
           {
               f1.listBox1.Items.Add(item.Name);
           }
      }

This compiles fine, but inside the API when using LoadLists(Form1 f1) it shows error Form1 is a type but used like a variable

Help would be appreciated, thanks