How to redirect Add to Cart link to product page?
Using Drupal Rules Module:

To redirect directly to checkout after a user clicks 'add to cart'


Admin -> Configure -> Rules -> Add New Rule
Give it a title of 'Add to Cart - Redirect to Checkout'
Set React on event to: After adding a product to the cart
Add new Action - set this to 'Page redirect'
Give it a value of 'checkout' and save.


Now when users click your add to cart button, they will be taken directly to checkout.  Alternatively, you can send them to /cart by change the value in step 5.