How to connect trial version of ATP to existing tenant?

In the process of enrolling into the trial version of ATP it would not allow me to use my existing tenant, but stated I could change this later. However, once stood up, I don't see how I can change the newly assigned tenant ID to match my existing tenant, hence I can't get the trial ATP to communicate with my paid subscription of Intune. 

If you stood up a trial version of ATP to connect to your current tenant, how did you do it? 

Thanks so much. -Alan