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