First of it is important that you know where you bought your wordpress template. We recommend you to follow this tutorial if you bought the template from TemplateMonster. If not you can follow the tutorial in the video above.
To disable the comment you need to download the disable comment plugin from the wordpress store, you can find the plugin here. Now you will recive a ZIP file in your download menu. Do not open the zip file but follow the instructions on the video. Upload the zipfile in the plugin area and activate the plugin. Now you can chose if you would like to enable or disable the comments.
Disable comments plugin
You can find the TemplateMonster tutorial here.