I don't see the creator's Instagram account
in my Ads Manager
First, please check to ensure that you do have admin access to the account, otherwise you will not be able to move forward with the campaign.

To do this, the account administrator can follow these steps:
Open Business Manager and click on the button Business Settings
On the left menu, admin should choose Accounts- Pages and then select the creator's page
After the admin selects the creator's page, click on Add People, and choose the manager that the account will be shared with.
Admin should give the manager access to Create Ads, and click Assign
After an admin completes these steps, you should then be able to create a Facebook Ad on behalf of the creator's account