Where do I put robots.txt?

At the root of your domain: https://example.com/robots.txt. Subdirectories are not crawled for it.

Does Disallow guarantee no indexing?

No. Crawlers won't crawl the URL but the URL itself can still appear in results. Use a noindex meta tag or HTTP header to truly block indexing.

No — Google ignores Crawl-delay; manage rate via Search Console. Bing and Yandex respect it.

Files never leave your device

Generate a properly-formatted robots.txt. Add user-agent rules, allow/disallow paths, link your sitemap, and copy the result.

User-agent

Disallow (one path per line)

Allow (one path per line)

Crawl-delay (seconds, optional)

Sitemap URL

robots.txt

User-agent: *
Allow: /admin/public/
Disallow: /admin/
Disallow: /private/

Sitemap: https://example.com/sitemap.xml

Add one block per user-agent.
List allow/disallow paths — one per line.
Optionally point to your sitemap and copy the result to /robots.txt on your server.