I am using zircon theme for my commerce site need to add cart and checkout pages to my site,how to create an add to cart button in drupal8 for product display which goes to cart page.
Wait until alpha3 is released, recreate your site, and use the core Add to Cart functionality on your product pages. Note: as we've been saying for some time, there is no alpha to alpha upgrade path, so you'll have to rebuild the site from scratch each time until we hit beta in late March.
Commerce 2 for Drupal 8 is now in Beta and we do have a cart to play with now, YAY. But adding a button for add to cart is not that clear.
I answered similar question here: https://drupal.stackexchange.com/a/239399/6488