Hi,
Google Ads automate targeting and bidding according to the specified goal and show ads based on the assets you provided for App Campaigns. You need to create an ad group and target the audience using specific criteria by following the steps in this guide via API. Then, for each logical set of assets, you could add an ad_group_ad with the corresponding ad for the campaign's advertising_channel_sub_type listed here. Let us know if you need any additional information.
Regards,
Nikisha Patel, Google Ads API Team