You can log in to your freshservice account using the Login option at the top-right on your freshservice Portal, which will be available in the URL - yourcompanyname.freshservice.com. This will take you to the login page where you can use your login credentials - email address and password, to access the helpdesk. Or if you have set up SSO, then it would redirect to the particular authentication and you would be able to login after entering the credentials.
In case you have a freshworks account, you can configure multiple modes of authentication to login to your account, such as SSO as well as using your freshworks credentials. This is especially suitable for logging in users from multiple domains