To create a DNN module , you first need to create a .dnn file which has information about the .ascx controls that your module will contain, for eg :-
<controls>
<control>DesktopModule\webControl1.ascx
</control>
</controls>
<files>
<file>DesktopModule\webControl1.ascx
</file>
<file>DesktopModule\webControl1.ascx.cs
</file>
<files></files></files>
this is how u can define ut web control in the .dnn file
u need to create a zip file of your module containing your .dnn file and the controls mentioned in your .ddn file
HTH