1.) Open "Integrations" in the administration of the corresponding project:

And click:

2) Click "Add New Account" to link a Google Account for the first time:

3.) Select the Google account associated with the desired Analytics profile:

4.) Allow contentbird access:

5.) Select the Google account in contentbird by clicking on the profile picture:

Then the profile picture appears selected and the "Account" dropdown becomes visible:

6.) Select the account name in the dropdown:

7.) Select the desired Analytics profile under "Profile":

8.) Save the settings you have made:

9.) After successful saving, the Google Analytics profile is integrated into the project:

Read here how to relink a Google account removed from contentbird.