Follow below steps to add Google Tag Manager(GTM) to Adobe Experience Manager(AEM),

Step 1. Create GTM Account and Web Container.

Step 2. Install AEM Core Components and Configure Data Layer.

Step 3. Set Up GTM Triggers and Variables.

Step 4. Test Integration in GTM Debugger.

Step 5. Set Up GA4 Account and Integration.

Step 6. Add GA4 Tags in GTM.

Step 7. Verify GA4 Events in Google Analytics.