Invoke guide and tell it to create new GUI, and give it the name form2 . Put all relevant controls in it. Save it as normal, with .fig and .m file.
Inside form1, you can use
handles.data_form2_will_need = whatever;
form2_h = form2();
to get the handle of form2 in order to communicate with it.
Inside the OpenFcn for form2 you can use,
handles.form1_h = findobj(groot, 'tag', 'form1');
handles1 = guidata(handles.form1_h);
handles.data_form2_needs = handles1.data_form2_will_need;