The portal is at portal.sigill.tech. Enter your email address in the Username or email field, then your password, then a one-time code from your authenticator app.
If your organisation uses Google Workspace, or Microsoft Entra ID (formerly Azure AD — the identity behind Microsoft 365, but also usable without it), you can instead use the Google or Microsoft button under Or sign in with, provided you have already been invited to Sigill using the same email address.
Two limits worth knowing. Microsoft sign-in accepts work and school accounts only — a personal outlook.com or hotmail.com account will not work. And if your organisation has no Google or Microsoft identity at all, nothing is lost: email and password with a one-time code works exactly the same.