Access doesn't do this natively (i.e. this is no such concept as "frames" or "panels", as there is in other languages). You can build a form which holds two Subform controls. The leftside subform control would always show your Menu, while the Rightside control would show whatever form you wish. You can change the form that's shown in a Subform by setting the SourceObject:
Me.YourSubformControl.SourceObject = "frmCustomers"
this would show a form named "frmCustomers" ...