How to allow scripts to affect visual effect graph

My project is 3D, using the experimental visual effects graph package. I’m trying to get a reference to a visual effect component so I can call visualeffect.play(). Right now any reference to a visual effect gets an error. I know I have to put something at the top near “using unity engine”, but what do I put up there? Thanks for your time!

using UnityEngine.VFX;