Whenever you sign up for windows hosting, plesk login URL with username and password always sent to you in welcome email but for your basic information am describing a way to Login into plesk:
Control Panel URL: http://yourdomainname.com:8880/
Secure Login URL : https://yourdomainname.com:8880/
To login click the link into your welcome email or type it into your browser give your username and password but be careful if you unintentionally copy any extra space while giving your password (this is a common mistake done by many users) and hit login.
So this is all you need to do.