Register your Igor as a Netatmo app at Netatmo "create an app" page and fill in the resulting details (Client ID and Client Secret) here. You should be able to login to dev.netatmo.com with the same username and password you use for the normal Netatmo dashboard.
Specify the following values:
Name: something with igor- is suggested
Description: doesn't really matter
App Website: not required
Company: leave blank
Company Website: leave blank
Data protection Officer name: your name
Data protection Officer email: your email
That will provide you with the details to enter in the following form.
Follow this link to trigger pulling data from the Fitbit cloud service into your Igor database.
The follow this link to view the data in the database. Check whether it conforms to your expectations.