Place the spring plate on the backing plate.

Be very careful not to move the heat sink while you install the screws.

Carefully thread one of the CPU heat sink screws slightly into the heat sink so that just a couple threads are engaged.

Press down on the opposite corner of the spring plate from where you just installed a screw.

While holding the corner down, thread another screw into that corner of the heat sink, again just tightening it until a couple threads are engaged.