How to implement google cdn

I have deployed my project on the google cloud. Now I need to implement google cdn. I deployed my project on the VM. I have created my VM directly without creating any "Instance template". I have checked on google to implement google cdn. and the steps are:

1- Create a health check 2- Create an instance group 3- Create a load balancer 4- Enable CDN

But at the point 2 for creating an instance group, I have to select an option "instance template". But I have deployed my project without creating any "Instance template".

1- If I create any new "Instance template" and select at the point 2 then if I enable cdn then will the cdn work for my existing VM (which was created without any instance template)? What should I do?

Thank you!

I agree with @Vega that the posted question here in SO should only be a programming question. Your question is more appropriate in serverfault

However to address this concern, Manage instance groups as per this documentation it lets you operate your application in a multiple identical VM instance. It has a feature of MIG services, including: autoscaling, autohealing, regional (multiple zone) deployment, and automatic updating, that is why the instance template is one of the options that is needed to configure.

I believe what you can do is Unmanaged instance group. This feature lets you manage the instances yourself. Upon deploying unmanaged instance group, there is an option wherein you can choose your created VM instance. To know more about unmanaged instance group and configuration you can use this link as a guidance.

After you create the unmanaged instance instance group, proceed with the creation of the load balancer and enable Cloud CDN.