How to create named volumes in Kubernetes?
k8s have documentation page about volumes and their types https://kubernetes.io/docs/concepts/storage/volumes/

So in short you need to define spec.volumes and spec.containers[].volumeMounts like:

apiVersion: v1
kind: Pod
metadata:
  name: test-pd
spec:
  containers:
  - image: gcr.io/google_containers/test-webserver
    name: test-container
    volumeMounts:
    - mountPath: /cache
      name: cache-volume
  volumes:
  - name: cache-volume
    emptyDir: {}