Adding another phone to 1 camera

We bought 1 camera to watch our dog while we were away. Everything works perfect (other then some buffering issues once and a while) but we can’t figure out how to add another phone to the camera. Everytime I tryto add it, it says “This product has already been registered.” Please help lol

I finally found someone that had the same question as me. Thank you anyways.

they have to sign in as you. Blink only allows one account/phone

More info at
This web based user manual has info regarding account setup, security, etc.