A. Click the Select Object button on the main toolbar and select the polygons as displayed in the following image. Draw a selection rectangle instead of clicking them because you need to select them on the other side too.


B. Scale the polygons up on the X and Y axis to increase the side of what will become the hole. At this point you may need to switch back to vertex sub-object level and move some vertexes to make sure the select polygons will become a clean circle after smoothing.


Click the small square button on the right of the Bridge button in the Edit Polygons section on the Modify tab to open the Bridge dialog box.

Change the number of Segments to 5.
Change the Taper value to: 0.0

Click OK to close the dialog box.