How to add fixed regressors in NARDL model

[Nadeem Sarwar]

Hi
My questions are on Nonlinear and Asymmetric Autoregressive Distribution Lag Model (NARDL)

1. How can we add fixed regressors (like dummies etc) in NARDL model?
2. If I have 3 variables on RHS, how can i check for Asymmetric relation w.r.t. one of these variables and symmetric relation wrt the other two variables?

Thanks