Instructions on how to COPY to docker container after creating a tarball?

Hey there - great action tool, thank you - I'm using this to copy an entire folder to a docker container without worrying about the details of ignore files for... reasons.   I tried archiving to `yolo.tar.gz` and then am attempting to `COPY yolo.tar.gz /app` but docker is reporting that the file `/yolo.tar.gz` is not found.  Ideas?