There were no configuration guides available for setting this up with FreePBX so I just played with the settings until I got something working without having to enable anonymous sip calls in.
Trunk Name: skype-trunk
The User Context value isn't terribly critical. I had it set to "anonymous" since the calls coming from skype come from firstname.lastname@example.org, but I felt like it was easier to identify the channels by using the userID skype provides. Also, the userid and secret are not skype credentials. They are values provided in the skype manager as your sip credentials when you sign up for skype to sip trunks using the skype connect service.