Comments are managed through a dedicated page in your Control Panel. You'll find it's very similar to editing entries or categories in Craft.
The left-hand sidebar groups all comments by the element they were made on.
You can filter the right-hand side table as you need to. It's especially useful to filter by a comments' status. You can also use the checkboxes on each row to update multiple comment's status at once.
Clicking on the first column will take you to the page where you can edit a comment. Here you can view all information regarding the comment, such as date, URL, IP Address, User Agent and more.
You are able to change a comment's text and status from this page.