Help with Machine Axis Definition for a Double-Column VTL with 5-Axis Head

I am currently configuring a double-column vertical lathe (VTL) and have encountered an issue that I need assistance with.

Machine Configuration:

Type: Double-column vertical lathe.

Right Side: Equipped with a tool holder for turning tools.

Left Side: Equipped with a 5-axis milling head.

Status: I have already set up the kinematics, travel limits, workpiece positions, and the rotary table fixture.

The Problem:
When I attempt to name the working axes, the selection window appears empty. Consequently, I am unable to proceed with the axis definition.

Questions:

How can I resolve the empty axis definition window?

What is the correct procedure to define and configure this specific dual-carriage (Turning/5-Axis Milling) machine to ensure proper functionality?

Thank you for your help.

Best regards,
Tomaž