Hi,
there are a few ways of doing this:
Additional information for 2.
You can use the tool modify -> snap together tool (open settings) and enabling snap to polygon face. Then you can select the face of the plane and from the cylinder and after hitting enter your plane is aligned to the face. Then moving your cylinder verts with vertex snapping and you have your square.
Regards,
LifeArtist
You could also apply a little arithmetic in the Component Editor, under the Polygon tab, to each of the 4 selected vertices.