You can find the login page by browsing to your website and adding /wp-login.php behind the URL. Is your webaddress example.org? Then you’ll find your login page at example.org/wp-login.php
On the login screen you can now fill in your username and password. You can check the checkbox to make the website remember your credentials, so you can log in automatically from now on. After logging in you’ll immediately navigate to the dashboard from where you can work on your website.