Hi @GillyP
Changing phone should make no difference, simply login to the Nest app and/or Google Home app using the same account you were using on your old phone in the same way you did on your old phone. If you were logging in with a Google account, do that, otherwise use the sign in with Nest option instead. Once signed in, your home and all your devices should already be there, no further action required.
That said, I see you selected Nest Learning Thermostat (1st gen), which is end of support and can no longer be controlled using the app.
End of support for Nest Learning Thermostats (1st & 2nd gen) - Google Nest Help
You can double check which thermostat model you have here:
How to tell which Nest thermostat you have - Google Nest Help
