Once you’ve created your custom image, you can either change the default values in the appropriate values file in the helm/alfresco-content-services folder, or you can override the values via the --set command-line option during the install:
helm install alfresco/alfresco-content-services --set repository.image.repository="yourRegistry" --set repository.image.tag="yourTag" --set share.image.repository="yourRegistry" --set share.image.tag="yourTag"