If you wish to disable all the comments on your entire website, this can be done from Dashboard > Theme Options. Here are the steps once you get there.
If you are looking to disable comments on all:
⋅ A － Pages - navigate to Theme Options > Pages > Show Comments - set to Off
⋅ B － Posts - navigate to Theme Options > Blog > Show Comments - set to Off
⋅ C － Portfolio - navigate to Theme Options > Portfolio > Show Comments - set to Off
In addition to this, each individual page/post/project can have its comments enabled/disabled.
To achieve this, simply go to the post in question from your backend. Once you are there, simply scroll down to the Discussion field. Here you should uncheck the Allow Comments box.
Another way to achieve this is to go to All Posts and click the Quick Edit next to a post. You will be able to see the Allow Comments box, which you should uncheck.