Please note: Effective August 31, 2019 Google has discontinued WorksWithNest integration support. Accounts that are logged in will continue to function normally, but no new sign-ins are possible. You may read more about it here.
As listed in the Nest integration support page , you will need to login to your Nest account (see step 5) . Since you are enabling this integration through your Awair app, there is no need to sign into your Awair account.
As listed in the Amazon Echo integration support page, you will need to enable the skill from the Alexa app, when you are in the app, you will need your Awair account info as listed in Step 4.