Link App Store
If you want to promote an app with Apple Search Ads, you must link to an App Store Connect account
You can link App Store Connect accounts to Apple Search Ads when you first create your account or when you create new campaign groups. If you have multiple App Store Connect accounts, you can link each one to your Apple Search Ads account to promote the associated apps. Or, if you have an agency account, you can create separate campaign groups for your clients and link them to each client’s App Store Connect account. Note that the payment method entered for the primary account will apply to all correlating campaign groups. Different payment methods can’t be entered for each campaign group.
Linking your App Store Connect account to your Apple Search Ads Advanced account lets you promote apps to the additional customer types “Returning users” and “Users of my other apps.” If you don’t link to an App Store Connect account, you won’t be able to promote an app with Apple Search Ads.
Note that you’ll need to be assigned the Legal Account Holder, App Manager, Admin, or Marketer role in App Store Connect and the Account Admin or Campaign Group Manager role in Apple Search Ads to link the accounts. You’ll also need to use the same email address to sign in for both.