All users can log into Codility at login.codility.com
First you need to provide your email address and then the system will find your user in the right instance. If your company doesn't use SSO as an authentication method, in the next step you will be asked to provide your password. If you use Google authentication, after providing your email address you will be prompted to authenticate through your Google account. If you have SAML SSO enabled and the right permissions assigned in your IDP, you will be logged in right away after providing your email address (given that your admin defined company domains for your account).