The WordPress login page URL is a big topic online for the simple reason that there are several different ones. You have to confirm if you would like to login to WordPress.com or a self-hosted install you downloaded.
Covering the most popular blog type on WordPress.com is what we will cover first. It generally is what the majority of bloggers are looking for if they have forgetten their URL for the WordPress login page on it. You can sign in at https://wordpress.com/wp-login.php?redirect_to=https%3A%2F%2Fwordpress.com%2F with your email or username for your blog that you previously have setup.
If you have forgotten your password, choose the Forgot Password to have a reset message and one time use link sent to the email address you registered with during setup. The lost password URL is https://wordpress.com/wp-login.php?action=lostpassword and you will be required to enter some basic information in the form that includes your username or email. Follow the instructions and click the blue Get New Password button to reset your login credentials.
Their is a entire guide on the official WordPress login page support located at http://en.support.wordpress.com/passwords/ that covers a longer tutorial. The quick reset guide above should work for most users. If you want to change your password and have already logged in, go to Personal Settings for your user account and do it there.
The next login to WordPress we will cover if you are using the self-hosted software and not the WordPress.com service. When you have downloaded a install package from WordPress.org or a service provided in your CPanel by your web hosting company and installed WordPress on your own server then you will have a different login URL to access the WP Admin interface. By default it will be located at http://yourdomain.com/wp-admin where you will want to replace the yourdomain text with your own domain name that is hosting your blog software installation.
This area is call the WP Admin and is short for WordPress Administration. This area looks exactly like the WordPress.com login page but is instead hosted on your own blog’s domain name. Your domain could end in .com, .net, .org, .co or a few hundred more types of extensions now available from registrars like GoDaddy. Be sure to replace the .com in the example above with your the extension that you are using to properly access the WordPress login page for your instance. Failure to do so will result in the page not working or not loading and either a 404 error or blank screen.