Getting your own certificate
By invitation, not by signing up — on purpose.
There is no sign-up page. A certificate you could create for yourself unprompted, with nobody else's say-so, would not be worth much to whoever reads it later — so the only way in is an invitation.
Who can send one
Only an entity that already holds a live certificate of its own. A counterparty who wants to onboard you sends the invitation from inside their own account; there's no public button that mints one. Being invited doesn't vouch for you, either — the inviter's belief about you confers nothing. You still verify yourself against the register independently, exactly as an uninvited entity would.
What happens when you open the link
You see who invited you, then verify your own company: your registration number, the officers the register names, and — depending on this deployment's identity policy — a document or a qualified signature establishing that you're really the person typing (see simulated identity if this deployment is running in demo mode). The certificate that comes out is yours: it works with every counterparty you choose to show it to afterwards, not only the one who invited you.
There's no mailer wired in yet, so an invitation link isn't emailed automatically — the inviter gets it back from their own account and passes it along themselves.