One of the most interesting features in WordPress compared to the other web authoring tool for web building is the comments feature. It creates a dynamic interactivity between you and your readers.
You can moderate your visitors’ comments via the Comments tab in the WordPress administrator panel. This means, even if you have set to allow comments, you can at any time unapprove any comments already posted and approved earlier on.
Various options are available for you to set for your Comments. They are listed under Options -> Discussion.
Most importantly as a beginner, you would want to allow comment. This is the place where you as the site administrator decide that and be sure that you press the Update options button once you have selected the option.
For more details with visual demonstration refer to the WordPress Tutorial.