A good first step is to read: https://larsroettig.dev/getting-started-with-magento-pwa-studio/
It will learn you to overwrite/extend PWA Studio default components. It's not the same as we did with LUMA. Now we use Scaffolding and the extensibility framework.
Please also have a look at: https://larsroettig.dev/getting-started-with-pwa-studio-extensibility/ for more about extensibility.
And watch: https://www.youtube.com/watch?v=5fTIYrGZH0M
Using the @magento/create-pwa project initializer is the fastest way to get a PWA Studio project set up for development. It is a user-friendly version of the create-project sub-command in the pwa-buildpack CLI tool.
yarn create @magento/pwa
Or with NPM:
npm init @magento/pwa
This command launches an interactive questionnaire in the command line for configuring different parts of the project.
Also interesting to read: https://github.com/fooman/venia-ui-override-resolver