Once a portal exists you need two things: the link to send out, and a way to see what your recipients will see.

You can copy a portal URL from either screen, and it is the same link.

Find the portal and click Copy Link. The URL goes to your clipboard.

Open the Portal option on the folder and click Copy URL.

Open the portal yourself first. It takes a few seconds and it catches the mistakes that are embarrassing to discover later: the wrong folder, content you did not mean to include, or a share with no expiry on it.

If you set a password, remember the recipient needs it, and sending it in the same message as the link defeats the point. Use a different channel.

Click the eye icon next to the portal.

Open the Portal option on the folder and click View Portal.

Anyone you send it to. A portal link works for whoever holds it, within whatever rules you set, so a forwarded link still opens unless a password or an expiry stops it.

That is not a flaw, it is what makes portals convenient. It is simply the reason expiry matters, and the reason password protection exists for anything sensitive.

Controlling who can get into a portal covers passwords and expiry. Monitoring and closing a portal covers seeing who opened it.