How to construct the NARX model.

How can be obtained the NARX model? using the custom regressors:

y(k-1)y(k-2),y(k-1)^2, y(k-2)^2,u(k-1)u(k-2),u(k-1)^2, u(k-2)^2.

Someone works with the NARX function of Matlab? I would like to know how to define the custom regressors in the NARX function.

Best regards

Edwin