In deployment.yaml at the path spec.template.spec.containers

It goes something like this

...
spec:
  containers:
    - name: {{ .Chart.Name }}
      image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
      imagePullPolicy: {{ .Values.image.pullPolicy }}
      env:         
        - name: JPDA_ADDRESS
          value: '*:8000'
...

So, once you run the above, if you do kubectl exec my-pod -c my-container -- "echo $JPDA_ADDRESS", it will print *:8000

It is important to understand, that Helm simply manages templates for Kubernetes objects. Helm's deployment.yaml produces a YAML spec for Kube object of kind: Deployment. So, if you want to know every possible field you can specify in deployment.yaml, you can run kubectl explain deployment --recursive anywhere you have kubectl running.