Canonical URL Meta Tag for a View Page
I'm assuming you're using Drupal 7.x and the latest alpha version of the Meta Tags module, correct? They are still working out the views integration functionality for this module but there is a sandbox project for this issue called 'meta tag views'. In Drupal 6.x nodewords, this was easier to do based upon path by just adding a custom entry at: /admin/content/nodewords/meta-tags/custom/add.

In the meantime, you can try the metatags_quick module which lets you assign meta tags to specific paths. You would need to add the 'canonical url' as a possible field but the interface is simple to use.