How to create AutoScalling Group using CDK for existing EC2 instance?

I have been exploring AWS-CDK recently and programming language I am using is Python. Since I am a newbie in this concept, I am trying to achieve one thing: How can I create AutoScaling Group for existing ec2 instance? I assume somewhere i need to mention the instance id, attached here by as one parameter to ASG.

Now what exact issue I am facing is, I am not able to understand how to pass the details of existing ec2 instance while configuring AutoScalingGroup. I am not creating VPC using CDK, instead I created one EC2 instance using console.

Any leads would be really helpful!!

Below is the code for AutoScalingGroup:

{ from constructs import Construct from aws_cdk import aws_autoscaling as autoscaling

from aws_cdk import (aws_ec2 as ec2, aws_ssm as ssm, Stack)

class AutoScalingStack(Stack): def init(self, scope:Construct, id: str,vpc: ec2.Vpc, **kwargs) -> None: super().init(scope,**kwargs)

autoscaling.AutoScalingGroup(self, "ASG",
vpc=vpc,
launch_template= launch_template

)

PS: I am unable to find AWS CDK tag.