As with the traditional Keyer, you load three clips into the Modular Keyer to create a key: a front clip, a back clip, and a key-in clip. You use the key-in clip, which is usually the same as the front clip, to create the matte for the front clip.
You can access the Modular Keyer from the Desktop, Action, and Batch. See Accessing the Colour Corrector and the Keyer from Action and Modular Keyer Node.
To access the Modular Keyer from the Desktop: