Here's a quick tutorial about how to post a comment. You only have to do this the first time:
1. Click on the Comments link below a blog post:
2. Type your comment, and click the "Select Profile" menu. It will show several choices. The easiest is probably the "Google Account" option, if you don't have an account of one of the other types. Select your choice and click the "Post Comment" button.
3. This will bring you to a Google sign-in page. If you already have a Google account, just sign in with your Google account information (the red box). If you do not have a Google account, click on the "Create a Google Acccount" link (the green box).
4. If you sign in with your Google account, skip to step 5. Otherwise, you'll be presented with the following screen. Fill out the information, using your normal, everyday email address. The weird looking word on the bottom is called a CAPTCHA, and it attempts to verify that you are human.
5. Once you click the orange "Continue" arrow at the bottom, you will be presented with a screen that looks like one of the ones below. Click "Post", and type in the CAPTCHA, if you have one. After this, you may need to sign in again, but you should not need to create another Google account.
6. After this, you should not need to register for a Google account again, but you may need to sign in again. Just use the directions, skipping step 5. If you click the "Stay signed in" checkbox in step 4, you will stay signed in indefinitely. Here's a picture:
Hope that helps with posting comments!