Hi,
First you need to ensure the licenses are available for the teams devices.
Follow: https://learn.microsoft.com/en-us/microsoftteams/rooms/admin-center-license-overview
Next you need to have a Resource account, that signs in to the devices.
Once these are setup, you can start signing into the device with the credentials.
Point to note: MFA causes issues while signin to the device and hence you need to have MFA removed on the resource account while you signin to the device.
Hope this helps.