Your title should show as <h1>Your Title</h1>. Tags after this should be <h2> through to <h6>.
Add alt tags to your content by adding simple HTML as follows <img src="Link to your image" alt="Description/keyword of your image"> You can also add a title for your image if users hover their mouse over the image <img src="Link to your image" alt="Description/keyword of your image" title="Your title">
An example of a robots.txt where the * after user-agent means all search engines can crawl the website and disallow for excluding pages. User-Agent: * Disallow: Sitemap: https://yourdomain.com/sitemap.xml