Install
Upload it under Plugins → Add New Plugin → Upload Plugin, then activate.
Install straight from GitHub with WP-CLI:
wp plugin install https://github.com/flyingkaktus/new-customer-discount-for-woocommerce/releases/download/v1.0.0/release.zipUpdates itself. It ships its own updater, so new versions appear under Dashboard → Updates.
Releases
2 releases. Each count is every asset in that release; expand a row for the breakdown.