How to add html robot meta tags to customize indexing?

These meta tags which direct the indexing and crawling of a page has to be specified in the header section of HTML code.

noindex, follow

• To avoid indexing a page but allow crawling the following meta tag has to be specified in the page that is crawled:
  <meta name="robots" content="noindex, follow">

index, nofollow

• To avoid crawling but allow indexing the following meta tag has to be specified:
  <meta name="robots" content="index, nofollow">

noindex, nofollow

• To avoid both indexing and crawling the following meta tag has to be provided:
  <meta name="robots" content="noindex, nofollow">

index, follow

• To index as well as crawl either you can avoid giving the meta robots or specify the same as shown:
  <meta name="robots" content="index, follow">

To learn about robots meta tags for customized indexing read: Using Robots meta tag in HTTP Collection