If you want to disable commenting by default in all new posts/pages, you should:
- Go to Admin > Settings > Discussion
- Uncheck “Allow link notifications from other blogs (pingbacks and trackbacks)”
- Uncheck “Allow people to post comments on new articles.”
- Click “Save Changes.”
If you have already created some posts/pages with comments enabled, you should:
- Go to each post/page > Edit
- Click Screen Options Panel and Check Discussion, then Uncheck the Discussion Settings that appear at the bottom of your page settings.