None of the directions, except clone and yarn install, work

When you try the first _yarn start_ command, it just says "Waiting for changes" and never returns to the command line.
If you kill that with Ctl+C, and move on to cd to example and then do Yarn start again, you get:
yarn start
yarn run v1.22.19
$ parcel index.html
/bin/sh: parcel: command not found
error Command failed with exit code 127.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

If you can please post correct documentation on how to build and start this service, that would be much appreciated.