You can open the phone at first by the guide of the video.
https://www.youtube.com/watch?v=53lkS6tlMtg
Then you can see that the SIM card slot is soldered on the logic board. So if you want to change a [http://www.witrigs.com/replacement-parts-sim-card-holder-sony-ericsson-xperia|new SIM card slot], you need professional solder machine to remove the old one and replace the new one.