As a registered user how do I make an entry on the site?

Summary of Roles

Administrator – Somebody who has access to all the administration features
Editor – Somebody who can publish posts, manage posts as well as manage other people’s posts, etc.
Author – Somebody who can publish and manage their own posts
Contributor – Somebody who can write and manage their posts but not publish posts
Subscriber – Somebody who can read comments/comment/receive news letters, etc.

There is a lot more information on the different roles in the WordPress Codex

When you first register you will be given authority as a Subscriber

This means that you have the ability to submit comments on posts and pages.

So how do I submit a comment?