Removing old camera and connecting new one to my account / how many devices does my plan cover?

I just replaced an outdoor camera/sensor light. It shows on the Ring menu under the other devices, but the new camera says it's in a trial period. How do I remove the old camera -I don't see it there anymore, so this might be moot - and add the new camera to my paid plan?Also, how can I tell how many devices my plan supports?Thx.