To create a new project based on this template using degit:
npx degit jeongtae/parcel-vanillajs-template my-app && cd $_
Note that you will need to have Node.js installed.
Install the dependencies with a package manager which you prefer:
npm install
# or
yarn install
Then you can start it in watch mode:
npm start
# or
yarn start
Navigate to http://localhost:1234 then you can see your app.
Edit the file in /src
and save it, then the page will be reload automatically to reflect changes.