If you are moving the vent from an existing room, then you would need to delete the vent from the previous room first. To do this:
With the Ecovent App, go into the room in which the vent is paired to and then click on the settings icon on the top right-hand corner.
Then disconnect the vent from the room. This will un-pair the vent from the sensor and allow it to be paired to another sensor.
To pair it to another sensor you will first need to reset the vent:
Take the magnetic center plate off.
Press down the small tab for 3/4 of a second (it's a very small button that sticks out on the flat surface of the box).
Wait until the light starts to blink red. It could take up to 3-4 seconds for it to start blinking. Blinking red light means that the vent is ready to be paired to another sensor. You can only pair one vent at a time, so make sure no more than one vent is blinking red.
With the Ecovent App, go into the room in which you would like the vent to be paired to and click on the settings icon on the top right-hand corner. This will take you to the room settings.
Press "add vent" and follow the instructions.