If you don't see button Create Campaign in your native ASA account, it means that you haven't linked your App Store Connect with it.
Note, that App Store Connect was previously called iTunes Connect.
In order to see the "Create my campaign" button, connect your App Store Connect account to your Search Ads Account. You can link when you first create an account, and when you create new campaign groups:
- Sign in to your Search Ads Advanced account to go to your Campaigns dashboard.
- Click on the blue down arrow at the top left of the screen above “Campaigns.”
- Click on Settings.
- Link your Search Ads Advanced account to your App Store Connect account.
- After the two accounts are linked, please clear your web browser’s cache and sign in.
Note that the App Store Connect Legal Account Holder, Admin, or Marketer, must hold either the Search Ads Account Admin or Campaign Group Manager role to link the App Store Connect account to the campaign group.
Here's a link to App Store Connect.
Here's what your account should look like: