Click the "New File" button in the toolbar or right‑click in the sidebar and choose "New File".

The live preview updates automatically when you edit an HTML file. Click "Run" to open in a new tab.

Yes, create them in the sidebar and link them in your HTML using normal <link> tags. The preview will inline them automatically.

Click the GitHub button, enter your repository name, commit message, and a personal access token (with 'repo' scope). The editor will push all files.