To connect an LED fixture to a DMX (Digital Multiplex) lighting control system, you'll need a few components and follow some basic steps:

1. DMX Controller: This is the device that sends DMX signals to control the lights. It could be a lighting console, software running on a computer, or a dedicated DMX controller device.

2. DMX Cable: DMX uses a specific type of cable for signal transmission. Standard DMX cables have 5 pins, but most modern fixtures use 3-pin XLR connectors. Make sure you have the appropriate cables for your fixtures.

3. LED Fixture: Ensure that your LED fixture supports DMX control. Most professional-grade LED fixtures come with DMX input/output ports.

Here are the steps to connect the LED fixture to the DMX system:

1. Set DMX Address: Each fixture on a DMX chain needs a unique address so the controller can communicate with it individually. This is usually set using dip switches or through a digital menu on the fixture itself. Refer to the fixture's manual to set the DMX address.

2. Connect the DMX Cable: Plug one end of the DMX cable into the DMX output port of your controller, and plug the other end into the DMX input port of the LED fixture. Ensure a secure connection.

3. Power On: Power on both the DMX controller and the LED fixture.

4. DMX Configuration: On your DMX controller, configure the channels corresponding to the functions you want to control on the LED fixture. For example, if the fixture has RGB color mixing, you might assign three consecutive DMX channels for red, green, and blue intensity control.

5. Test and Control: Once configured, you should be able to control the LED fixture using the DMX controller. Test various functions such as color, intensity, strobing, and effects to ensure everything is working as expected.

6. Daisy-Chaining: If you have multiple fixtures, you can daisy-chain them together by connecting the output of one fixture to the input of the next. Make sure to set each fixture to a unique DMX address.

7. Termination (Optional): If you're experiencing signal issues or flickering lights, you might need to terminate the DMX chain. This involves adding a terminator (a resistor) to the last fixture in the chain. Consult your DMX controller's manual for instructions on termination.

By following these steps, you should be able to successfully connect and control your LED fixture using a DMX lighting control system. Always refer to the manuals provided with your equipment for specific instructions and troubleshooting tips.