I'll just post what I sent you in a support ticket earlier.
We currently do not have a step by step guide for setting up the K-Mix apart from the section of the manual that covers the virtual HUI port in the Editor. You can use this to emulate Mackie control surfaces and provides you with some mixing/transport functionality. Add a Mackie control surface in Logic X, and then follow the steps listed on page 125 of the manual to set up the K-Mix to send the proper messages.
I am actually in the process of putting a blog post together that will cover setting up the K-Mix as a control surface with Logic from the ground up. It's a bit of work, but allows you for tight and fairly customizable integration. Stay tuned for that near the end of the week!