Prepare the header strip:
Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - long pins down.
Add the MLX90393:
Place the board over the pins so that the short pins poke through the top of the breakout pads.
Be sure to solder all pins for reliable electrical contact.
(For tips on soldering, be sure to check out the Guide to Excellent Soldering).
OK, you're done!
You can now plug in your Magnetometer and start measuring some magnetic fields!