In order to log in to your WordPress blog, you need to access WordPress login page or WordPress admin page. This should be quite easy, you just need to type address of these pages like this:
WordPress login page: myblog.com/wp-login.php
WordPress admin page: myblog.com/wp-admin
Both pages are pretty much the same page, but you can access it in different ways. It is also good idea to hide the address of your login page to something else, so that it can’t be easy accessible by potential attackers. You can hide it by using .htaccess file
or even using some third party plugin that can do that automatically for you. In any case, you would have the access to the login page, but the URI will be different. These are some of the examples how it could look like:
This is good protection for potential attackers. Even they know that your site is created in WordPress, they will not have any idea how to access your WordPress login page.