Two parts, for the chart itself, you can download the chart tar file and upload to a specific location on the k3s server, then reference it with something like https://%{KUBERNETES_API}%/static/charts/the_chart_tar_file.

2ndly, for the container images, you can pull the image, docker save as tar files and upload to a specific location on the k3s server.

Refer to https://github.com/rancher/k3s#air-gap-support for more details.

But the location of the directory need be validated. I believe it is not updated for v0.6.1