It appears that you are talking about the calendar control which is a control
not a "form" and you need to place it on a form in order to use it. Similar
to the way you add a text box control.
You can use the Calendar ActiveX Control that ships with your
Access program. You'll find it under your ActiveX Controls list.
To help you see how this works I suggest you go to Arvin Meyer's
site and download a couple of his sample databases that demonstrate
how to use the calendar.