I was trying to set up my signature for my Apex, followed all the steps, filled everything in and click the Add Signature button to only get this message...."Signature save failed. Sig already exist."  Just curious what I did wrong or how to fix this.  Any help??  

You must have hit 'add' twice. It does exist, and is at the bottom of the list. It was empty, so I added some text so that you can find it.