To make a CNC retrofit, which involves upgrading an existing machine with computer numerical control capabilities, follow these general steps:

1. Evaluate your machine: Assess the mechanical and electrical aspects of your machine, including its structure, motors, controllers, and other components. Determine its compatibility with a CNC retrofit.
   
2. Select a control system: Research and determine the appropriate control system for your machine based on factors such as your budget, required capabilities, and compatibility with your machine. There are various options available, such as Mach3, LinuxCNC, or proprietary controller software.

3. Prepare the mechanical components: Ensure that your machine's mechanical components, including linear motion systems, are in good condition or replace them if necessary. Make any modifications needed to accommodate the CNC retrofit.

4. Upgrade the electrical components: Replace the machine's existing control system, such as relay logic or outdated CNC controls, with the new CNC control system. Install and wire the new components, including motor drivers, stepper or servo motors, and any additional sensors or switches needed.

5. Install the control software: Install and configure the chosen CNC control software onto a computer or dedicated controller. Connect the computer or controller to the new control system and set up communication between them.

6. Calibrate and test: Calibrate the CNC retrofit by configuring the software settings, setting up the axis steps and resolutions, and determining other parameters specific to your machine. Test the machine's movements and functions to ensure everything is working correctly.

7. Learn the software: Familiarize yourself with the CNC control software and its features. Learn how to program your machine, create tool paths, and execute operations safely and efficiently.

8. Start using your retrofit CNC machine: Once all the steps are complete, you can start using your upgraded machine. Begin with simple projects to get comfortable with the new controls and gradually tackle more complex tasks.

Note: The process and specific steps may vary depending on the machine and control system you choose. It is important to carefully follow the manufacturer's instructions and seek expert help if needed.