In Access when you create a new form using one of the form tools on the create tab or when you add fields to a form while it is open in layout view, access puts boxes and other control in guides called layouts.
Well you can adjust the size of the form controls by clicking and dragging them or by using the property sheet to specify an exact value. Here is how it is to be done.
Select one control by clicking on it. For selecting a block of contiguous controls i.e controls that are next to each other or on the top of each other.
After then select the first control, then hold the shift key down and select the last control. In order to select non-contiguous controls, you need to use CTRL key instead.