The way it works is very simple. When you signup to coComment, you are given a bookmarklet that you are asked to add to your browser. Then, the next time you come across a blog post that you want to comment on, click on the bookmarklet before commenting. You will then see coComment logo and your username come up next to the submit button of the comment form to show that it has been enabled (clicking on it will show information about coComment). Click on submit and you will see a message saying that coComment has processed the comment and added it to your conversation page.
Once you have used coComment to track comments on a blog, you will then be able to track it in the “Your Conversations” section. The conversations section will show a list of every post that you have used coComment on.