Register an app on spotify to get a Client ID here https://developer.spotify.com/dashboard.
On the dashboard, open the edit settings and add http://localhost:3000 as Redirect URIs
On Spotify Dashboard, copy the Client ID of the app that is just created
Copy .env.example to .env
Paste the Client ID into the .env file as value of VITE_CLIENT_ID
Run npm install
Run npm run dev