Thanks for the interest, glad you hear you are wanting to get Launch running on your AEM instance. AEM 6.3 had a native integration with DTM and 6.4 has one with Launch. If upgrading to v6.4 is not an option right now, you can contact your AEM account representative about requesting a new Feature Pack be back ported to a prior version.
Could you maybe also tell me what the actual integration does? Does it import the js files into AEM or does it still write out the CND url
The AEM 6.4/Launch integration allows you to both self-host the files or reference them on Adobe's CDN. In addition to the URL Jantzen.Belliston posted, you might also find these videos useful:
If you are using 6.3 with Launch, I suggest using Adobe's CDN and just pasting the embed codes in your global header and footer (if using sync embed codes).
I followed this tutorial for 6.4. I verified token successfully and see Launch added dtm script in we-retail header automatically after the configuration.
Is there any way to debug this why the alert is not being shown
If you see the Launch embed codes in the we-retail source code you are almost there! Do you see the correct Launch property details when you open the Experience Cloud Debugger? Adobe Experience Cloud Debugger - Chrome Web Store
If not, check the Network tab in your Dev Tools to make sure the Launch js file is loading. If there is a 404 error, it's usually because you haven't published anything to the Environment whose embed code URL you are using.