Adding twitter cards on your website is not a big deal; you can easily add Twitter cards to your website in just 2 minutes. In order to add Twitter summary card you need to follow the given steps -
1. Define the Card type - <meta name="twitter:card" content="summary"/>
2. Then, give the username of the account the card should be attributed to - <meta name="twitter:site" content="@username"/>
3. Then, provide the title(under 70 characters) of the content page. - <meta name="twitter:title" content="Title of your webpage"/>
4. Provide a description(200 characters) to summarize your content page properly.
5. Then, give the URL of the image to appear on the twitter card - <meta name="twitter:image" content="image URL"/>
For more read - https://allinsider.net/twitter-card-validator/