Now just add some flux onto the side of the shield where it rests on top of a pad, and minding the surrounding SMD components (DON'T poke any of them with your iron), solder the shield into place.

If you have insufficient heat, try placing the side of the iron along the side of the sim-reader shield's side. This way heat will conduct onto the larger metal part faster. Don't hold the iron there too long though, excess heat on the plastic parts is never good.

A good trick is to keep you SIM card inside the reader while doing this. This way even if you melt the plastic a little, the card will still fit inside.