You have what Rockshox call a "maxle" You need some metric allen keys and the hope that the maxle hasn't stuck itself to your forks.
You need to undo one side of the maxle which when wound out is similar looking to a quick release skewer. Don't wind this all the way out, just loosen it. This takes the pressure off the tube that makes up the other half of the maxle which is split at one end to tighten it onto your forks when you do the smaller skewer type fitting.
Once one side is loosened you will need to simply slide the maxle out the other side. This is where you'll find out if it is stuck and needs man handling. A rubber mallet should move it if it plays stubborn but try not to bugger it, you won't get any smiles from it if you do!
Once you've figured it out, put it back together and pull it apart a few times to get the gist of it. Put some grease where you need it and you're laughing!